As filed with the Securities and Exchange Commission on May 19, 2006

Registration No. 333-          

UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form S-3

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

The Williams Companies, Inc.

(Exact Name of Registrant as Specified in Its Charter)

One Williams Center

Tulsa, Oklahoma 74172

(918) 573-2000

(Address, Including Zip Code, and Telephone Number, Including Area Code, of Registrant’s Principal Executive Offices)

James J. Bender, Esq.

Senior Vice President and General Counsel

One Williams Center, Suite 4900

Tulsa, Oklahoma 74172

(918) 573-2000

(Name, Address, Including Zip Code, and Telephone Number, Including Area Code, of Agent for Service)

With a copy to:

Gibson, Dunn & Crutcher LLP

1801 California Street, Suite 4100

Denver, Colorado 80202-2642

(303) 298-5700

Attention: Richard M. Russo, Esq.

     Approximate date of commencement of proposed sale to the public: From time to time after the effective date of this registration statement.

     If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box.    o

     If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box.    þ

     If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    o

     If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    o

     If this Form is a registration statement pursuant to General Instruction I.D. or a post-effective amendment thereto that shall become effective upon filing with the Commission pursuant to Rule 462(e) under the Securities Act, check the following box.    þ

     If this Form is a post-effective amendment to a registration statement filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, check the following box.    o

CALCULATION OF REGISTRATION FEE

PROSPECTUS

THE WILLIAMS COMPANIES, INC.

DEBT SECURITIES

PREFERRED STOCK

COMMON STOCK

PURCHASE CONTRACTS

WARRANTS

UNITS

        We or selling securityholders to be named in a prospectus supplement may from time to time offer to sell debt securities, preferred stock, common stock, purchase contracts, warrants or units. Each time we or a selling securityholder sells securities pursuant to this prospectus, we will provide a supplement to this prospectus that contains specific information about the offering and the specific terms of the securities offered. You should read this prospectus and the applicable prospectus supplement and the documents incorporated by reference herein and therein carefully before you invest in our securities.

      Our common stock is listed on the New York Stock Exchange under the ticker symbol “WMB.”

      We will sell these securities directly to investors, or through agents, dealers or underwriters as designated from time to time, or through a combination of these methods, on a continuous or delayed basis.

      This prospectus may not be used to sell our securities unless it is accompanied by the applicable prospectus supplement.

      You should rely only on the information incorporated by reference or provided in this prospectus or any prospectus supplement. We have not authorized anyone else to provide you with different information or to make additional representations. We are not making or soliciting an offer of any securities other than the securities described in this prospectus and any prospectus supplement. We are not making or soliciting an offer of these securities in any state or jurisdiction where the offer is not permitted or in any circumstances in which such offer or solicitation is unlawful. You should not assume that the information contained or incorporated by reference in this prospectus or any prospectus supplement is accurate as of any date other than the date on the front of those documents.

      Investing in our securities involves a high degree of risk. See “Risk Factors” contained in the applicable prospectus supplement and in the documents incorporated by reference herein and therein.

      Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representations to the contrary are a criminal offense.

The date of this prospectus is May 19, 2006.

TABLE OF CONTENTS

ABOUT THIS PROSPECTUS

      This prospectus is part of a registration statement we filed with the Securities and Exchange Commission (“SEC”) using a “shelf” registration process. We or selling securityholders to be named in a prospectus supplement may sell any combination of the securities described in this prospectus from time to time, either separately or in units, in one or more offerings.

      Each time we or selling securityholders sell securities pursuant to this prospectus, we will describe in a prospectus supplement, which will be delivered with this prospectus, specific information about the offering and the terms of the particular securities offered.

      In addition, the prospectus supplement may also add, update or change the information contained in this prospectus. If there is any inconsistency between the information contained in this prospectus and any information incorporated by reference herein, on the one hand, and the information contained in any applicable prospectus supplement or incorporated by reference therein, on the other hand, you should rely on the information in the applicable prospectus supplement or incorporated by reference therein.

      Wherever references are made in this prospectus to information that will be included in a prospectus supplement, to the extent permitted by applicable law, rules or regulations, we may instead include such information or add, update or change the information contained in this prospectus by means of a post-effective amendment to the registration statement of which this prospectus is a part, through filings we make with the SEC that are incorporated by reference into this prospectus or by any other method as may then be permitted under applicable law, rules or regulations.

      In this prospectus, Williams (which includes The Williams Companies, Inc. and, unless the context otherwise requires, all of our subsidiaries) is at times referred to in the first person as “we,” “us” or “our.” We also sometimes refer to Williams as the “Company.”

WHERE YOU CAN FIND MORE INFORMATION

      We file annual, quarterly and current reports, proxy statements and other information with SEC. You may read and copy any reports, statements or other information that we file with the SEC at the SEC’s public reference room located at 100 F Street, N.E., Washington D.C. 20549. You may obtain information on the operation of the public reference room by calling the SEC at 1-800-SEC-0330.

      The SEC maintains a website on the Internet at http://www.sec.gov that contains reports, proxy and information statements and other information regarding us. The reports, proxy and information statements and other information regarding Williams can be downloaded from the SEC’s website. Unless specifically listed under “Incorporation by Reference” below, the information contained on the SEC website is not intended to be incorporated by reference in this prospectus and you should not consider that information a part of this prospectus.

      Our SEC filings can also be inspected and copied at the offices of the New York Stock Exchange, 20 Broad Street, New York, New York 10005. You may also inspect our SEC reports on our website at http://www.williams.com. Information contained on our website is not intended to be incorporated by reference in this prospectus and you should not consider that information a part of this prospectus.

INCORPORATION BY REFERENCE

      We are incorporating by reference into this prospectus information we file with the SEC, which means we are disclosing important information to you by referring you to those documents. The information we incorporate by reference is considered to be part of this prospectus, unless we update or supersede that information by the information contained in this prospectus or the information we file subsequently that is

incorporated by reference into this prospectus or any prospectus supplement. We are incorporating by reference the following documents that we have filed with the SEC:

      All documents that we file with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) after the date of this prospectus and prior to the termination of all offerings made pursuant to this prospectus also will be deemed to be incorporated herein by reference and will automatically update and supersede information in this prospectus. Nothing in this prospectus shall be deemed to incorporate information furnished to but not filed with the SEC pursuant to Item 2.02 or Item 7.01 of Form 8-K (or corresponding information furnished under Item 9.01 or included as an exhibit).

      Statements made in this prospectus, in any prospectus supplement or in any document incorporated by reference in this prospectus or any prospectus supplement as to the contents of any contract or other document are not necessarily complete. In each instance we refer you to the copy of the contract or other document filed as an exhibit to the registration statement of which this prospectus is a part or as an exhibit to the documents incorporated by reference.

      We will provide to you, at no cost, a copy of any document incorporated by reference in this prospectus and any exhibits specifically incorporated by reference in those documents. You may request copies of these filings from us by mail at the following address, or by telephone at the following telephone number:

The Williams Companies, Inc.

Investor Relations

One Williams Center

Tulsa, Oklahoma 74172

Telephone Number: (918) 573-2000

FORWARD-LOOKING STATEMENTS

      Certain matters contained or incorporated by reference in this prospectus include forward-looking statements — statements that discuss our expected future results based on current and pending business operations. We make these forward-looking statements in reliance on the safe harbor protections provided under the Private Securities Litigation Reform Act of 1995.

      All statements, other than statements of historical facts, included or incorporated by reference in this prospectus which address activities, events or developments that we expect, believe or anticipate will exist or may occur in the future, are forward-looking statements. Forward-looking statements can be identified by various forms of words such as “anticipates,” “believes,” “could,” “may,” “should,” “continues,” “estimates,” “expects,” “forecasts,” “might,” “planned,” “potential,” “projects,” “scheduled” or similar expressions. These forward-looking statements include, among others, statements regarding:

      Forward-looking statements are based on numerous assumptions, uncertainties and risks that could cause future events or results to be materially different from those stated or implied in this prospectus or in the documents incorporated herein by reference. Given the uncertainties and risk factors that could cause our actual results to differ materially from those contained in any forward-looking statement, we caution investors not to unduly rely on our forward-looking statements. We disclaim any obligation to update the above list or to announce publicly the result of any revisions to any of the forward-looking statements to reflect future events or developments. Further, the information about our intentions contained or incorporated by reference in this prospectus or any prospectus supplement represents our intentions as of the date of this prospectus or any prospectus supplement, as applicable, or the date of such document incorporated by reference herein or therein, as applicable, and is based on, among other things, the existing regulatory environment, industry conditions, market conditions and prices, the economy in general and our assumptions as of such date. We may change our intentions, at any time and without notice, based upon any changes in such factors, in our assumptions, or otherwise.

THE COMPANY

      We are a natural gas company originally incorporated under the laws of the State of Nevada in 1949 and reincorporated under the laws of the State of Delaware in 1987. We were founded in 1908 when two Williams brothers began a construction company in Fort Smith, Arkansas.

      Today, we primarily find, produce, gather, process, and transport natural gas. We also manage a wholesale power business. Our operations are concentrated in the Pacific Northwest, Rocky Mountains, Gulf Coast, Southern California and Eastern Seaboard.

      Our business segments include Power, Gas Pipeline, Exploration & Production, Midstream, and Other. See “Business — Business Segments” in Item 1 of Part I of the 2005 Form 10-K for a more detailed description of assets owned and services provided by each of our business segments.

      Our principal executive offices are located at One Williams Center, Tulsa, Oklahoma 74172, and our telephone number is (918) 573-2000.

USE OF PROCEEDS

      We intend to use the net proceeds we receive from the sale of securities by us as set forth in the applicable prospectus supplement. Unless otherwise specified in the applicable prospectus supplement, we will not receive any proceeds from the sale of securities by selling securityholders.

RATIO OF EARNINGS TO FIXED CHARGES

      The following table sets forth the Company’s consolidated ratio of earnings to fixed charges for the three months ended March 31, 2006 and the five years ended December 31, 2005.

DESCRIPTION OF DEBT SECURITIES

      The following sets forth certain general terms and provisions of the base indenture under which the debt securities are to be issued, unless otherwise specified in a prospectus supplement. The particular terms of the debt securities to be sold will be set forth in a prospectus supplement relating to such debt securities.

      The debt securities will represent unsecured general obligations of the Company, unless otherwise provided in the prospectus supplement. As indicated in the applicable prospectus supplement, the debt securities will either be senior debt or subordinated debt. Unless otherwise specified in the applicable prospectus supplement, the debt securities will be issued under an indenture to be entered into between us and JPMorgan Chase Bank, N.A. that has been filed as an exhibit to the registration statement of which this prospectus is a part, subject to such amendments or supplemental indentures as are adopted from time to time. The following summary of certain provisions of that indenture does not purport to be complete and is subject to, and qualified in its entirety by, reference to all the provisions of that indenture, including the definitions therein of certain terms. Wherever particular sections or defined terms of the indenture are referred to, it is intended that such sections or defined terms shall be incorporated herein by reference.

General

      The indenture does not limit the amount of debt securities that may be issued thereunder. The applicable prospectus supplement with respect to any debt securities will set forth the following terms of the debt securities offered pursuant thereto:

      Debt securities may be presented for exchange, conversion or transfer in the manner, at the places and subject to the restrictions set forth in the debt securities and the prospectus supplement. Such services will be provided without charge, other than any tax or other governmental charge payable in connection therewith, but subject to the limitations provided in the indenture.

      The indenture does not contain any covenant or other specific provision affording protection to holders of the debt securities in the event of a highly leveraged transaction or a change in control of the Company, except to the limited extent described below under “— Consolidation, Merger and Sale of Assets.” The Company’s certificate of incorporation also contains other provisions which may prevent or limit a change of control. See “Description of Capital Stock.”

Modification and Waiver

      The indenture provides that supplements to the indenture and the applicable supplemental indentures may be made by the Company and the trustee for the purpose of adding any provisions to or changing in any manner or eliminating any of the provisions of the indenture or of modifying in any manner the rights of the holders of debt securities of a series under the indenture or the debt securities of such series, with the consent of the holders of a majority (or such greater amount as is provided for a particular series of debt securities) in principal amount of the outstanding debt securities issued under such indenture that are affected by the supplemental indenture, voting as a single class; provided that no such supplemental indenture may, without the consent of the holder of each such debt security affected thereby, among other things:

      The indenture provides that a supplemental indenture that changes or eliminates any covenant or other provision of the indenture that has expressly been included solely for the benefit of one or more particular series of debt securities, or that modifies the rights of the holders of such series with respect to such covenant or other provision, shall be deemed not to affect the rights under the indenture of the holders of debt securities of any other series.

      The indenture provides that the Company and the applicable trustee may, without the consent of the holders of any series of debt securities issued thereunder, enter into additional supplemental indentures for one of the following purposes:

Events of Default

      Unless otherwise provided in any prospectus supplement, the following will be events of default under the indenture with respect to each series of debt securities issued thereunder:

      In case an event of default specified in clause (a) or (b) above shall occur and be continuing with respect to any series of debt securities, holders of at least 25%, and in case an event of default specified in any clause other than clause (a), (b) or (e) above shall occur and be continuing with respect to any series of debt securities, holders of at least a majority, in aggregate principal amount of the debt securities of such series then outstanding may declare the principal (or, in the case of discounted debt securities, the amount specified in the terms thereof) of such series to be due and payable. If an event of default described in (e) above shall occur and be continuing then the principal amount (or, in the case of discounted debt securities, the amount specified in the terms thereof) of all the debt securities outstanding shall be and become due and payable immediately, without notice or other action by any holder or the applicable trustee, to the full extent permitted by law. Any event of default with respect to particular series of debt securities under such indenture may be waived by the holders of a majority in aggregate principal amount of the outstanding debt securities of such series, except in each case a failure to pay principal of or premium, interest or additional amounts, if any, on such debt securities or a default in respect of a covenant or provision which cannot be modified or amended without the consent of each holder affected thereby.

      The indenture provides that the applicable trustee may withhold notice to the holders of any default with respect to any series of debt securities (except in payment of principal of or interest or premium on, or sinking fund payment in respect of, the debt securities) if the applicable trustee considers it in the interest of holders to do so.

      The indenture contains a provision entitling the applicable trustee to be indemnified by the holders before proceeding to exercise any trust or power under the indenture at the request of such holders. The indenture provides that the holders of a majority in aggregate principal amount of the then outstanding debt securities of any series may direct the time, method and place of conducting any proceedings for any remedy available to the applicable trustee or of exercising any trust or power conferred upon the applicable trustee with respect to

the debt securities of such series; provided, however, that the applicable trustee may decline to follow any such direction if, among other reasons, the applicable trustee determines in good faith that the actions or proceedings as directed may not lawfully be taken or would be unduly prejudicial to the holders of the debt securities of such series not joining in such direction. The right of a holder to institute a proceeding with respect to a series of debt securities will be subject to certain conditions precedent including, without limitation, that in case of an event of default specified in clause (a), (b) or (e) of the first paragraph above under “— Events of Default,” holders of at least 25%, or in case of an event of default other than specified in clause (a), (b) or (e) of the first paragraph above under “— Events of Default,” holders of at least a majority, in aggregate principal amount of the debt securities of such series then outstanding make a written request upon the applicable trustee to exercise its powers under such indenture, indemnify the applicable trustee and afford the applicable trustee reasonable opportunity to act. Notwithstanding the foregoing, the holder has an absolute right to receipt of the principal of, premium, if any, and interest when due on the debt securities, to require conversion of debt securities if such indenture provides for convertibility at the option of the holder and to institute suit for the enforcement thereof.

Consolidation, Merger and Sale of Assets

      The indenture provides that the Company may not directly or indirectly consolidate with or merge with or into, or sell, assign, transfer, lease, convey or otherwise dispose of all or substantially all of its assets and properties and the assets and properties of its subsidiaries (taken as a whole) to another person in one or more related transactions unless the Company survives or the successor person is a person organized under the laws of any domestic jurisdiction and assumes the Company’s obligations on the debt securities issued thereunder, and under the indenture, and after giving effect thereto no event of default, and no event that, after notice or lapse of time or both, would become an event of default, shall have occurred and be continuing, and that certain other conditions are met.

Certain Covenants

      Payment of Principal, any Premium, Interest or Additional Amounts. The Company will duly and punctually pay the principal of, and premium and interest on or any additional amounts payable with respect to, any debt securities of any series in accordance with their terms.

      Maintenance of Office or Agency. The Company will be required to maintain an office or agency in each place of payment for each series of debt securities for notice and demand purposes and for the purposes of presenting or surrendering debt securities for payment, registration of transfer, or exchange.

      Reports. So long as any debt securities of a particular series are outstanding, the Company will file with the Trustee, within 30 days after the Company is required to file the same with the Commission, copies of the annual reports and of the information, documents and other reports (or copies of such portions of any of the foregoing as the Commission may from time to time by rules and regulations prescribe) which the Company may be required to file with the Commission pursuant to Section 13 or Section 15(d) of the Exchange Act; or, if the Company is not required to file information, documents or reports pursuant to either of said Sections, then it shall file with the Trustee and the Commission, in accordance with rules and regulations prescribed from time to time by the Commission, such of the supplementary and periodic information, documents and reports which may be required pursuant to Section 13 of the Exchange Act in respect of a security listed and registered on a national securities exchange as may be prescribed from time to time in such rules and regulations.

      Additional Covenants. Any additional covenants of the Company with respect to any series of debt securities will be set forth in the prospectus supplement relating thereto.

Conversion Rights

      The terms and conditions, if any, upon which the debt securities are convertible into common stock or preferred stock will be set forth in the applicable prospectus supplement relating thereto. Such terms will include the conversion price (or manner of calculation thereof), the conversion period, provisions as to

whether conversion will be at the option of the holders or the Company, the events requiring an adjustment of the conversion price and provisions affecting conversion in the event of redemption of such debt securities and any restrictions on conversion.

Redemption; Repurchase at the Option of the Holder; Sinking Fund

      The terms and conditions, if any, upon which (a) the debt securities are redeemable at the option of the Company, (b) the holder of debt securities may cause the Company to repurchase such debt securities or (c) the debt securities are subject to any sinking fund will be set forth in the applicable prospectus supplement relating thereto.

Repurchases on the Open Market

      The Company or any affiliate of the Company may at any time or from time to time repurchase any debt security in the open market or otherwise. Such debt securities may, at the option of the Company or the relevant affiliate of the Company, be held, resold or surrendered to the trustee for cancellation.

Discharge, Defeasance and Covenant Defeasance

      The indenture provides, with respect to each series of debt securities issued thereunder, that the Company may satisfy and discharge its obligations under such debt securities of a series and such indenture with respect to debt securities of such series if:

      Notwithstanding such satisfaction and discharge, the obligations of the Company to compensate and indemnify the trustee, to pay additional amounts, if any, in respect of debt securities in certain circumstances and to convert or exchange debt securities pursuant to the terms thereof and the obligations of the Company and the trustee to hold funds in trust and to apply such funds pursuant to the terms of the indenture, with respect to issuing temporary debt securities, with respect to the registration, transfer and exchange of debt securities, with respect to the replacement of mutilated, destroyed, lost or stolen debt securities and with respect to the maintenance of an office or agency for payment, shall in each case survive such satisfaction and discharge.

      Unless inapplicable to debt securities of a series pursuant to the terms thereof, the indenture provides that (i) the Company will be deemed to have paid and will be discharged from any and all obligations in respect of the debt securities issued thereunder of any series, and the provisions of such indenture will, except as noted below, no longer be in effect with respect to the debt securities of such series (“legal defeasance”) and (ii) (1) the Company may omit to comply with the covenant under “— Consolidation, Merger and Sale of Assets” and any other additional covenants established pursuant to the terms of such series, and such omission shall be deemed not to be an event of default under clause (c) or (f) of the first paragraph of

“— Events of Default” and (2) the occurrence of any event described in clause (f) of the first paragraph of “— Events of Default” shall not be deemed to be an event of default, in each case with respect to the outstanding debt securities of such series; provided that the following conditions shall have been satisfied with respect to such series:

      Notwithstanding a legal defeasance, the Company’s obligations with respect to the following in respect of debt securities of such series will survive with respect to such securities until otherwise terminated or discharged under the terms of the indenture or until no debt securities of such series are outstanding:

Applicable Law

      The indenture provides that the debt securities and the indenture will be governed by and construed in accordance with the laws of the State of New York.

About the Trustee

      Unless otherwise specified in the applicable prospectus supplement, JPMorgan Chase Bank, N.A. is the trustee under the indenture.

DESCRIPTION OF CAPITAL STOCK

Preferred Stock

      Under our restated certificate of incorporation, as supplemented, we are authorized to issue up to 30,000,000 shares of preferred stock, par value $1.00 per share, in one or more series. As of May 15, 2006, there were no shares of preferred stock issued and outstanding.

      The following description of preferred stock sets forth certain general terms and provisions of the series of preferred stock to which any prospectus supplement may relate. The prospectus supplement relating to a particular series of preferred stock will describe certain other terms of such series of preferred stock. If so indicated in the prospectus supplement relating to a particular series of preferred stock, the terms of any such series of preferred stock may differ from the terms set forth below. The description of preferred stock set forth below and the description of the terms of a particular series of preferred stock set forth in the related prospectus supplement are not complete and are qualified in their entirety by reference to the certificate of incorporation and to the certificate of designation relating to that series of preferred stock.

      The rights of the holders of each series of preferred stock will be subordinate to those of our general creditors.

      The certificate of incorporation will set forth the designations, preferences, and relative, participating, optional and other special rights, and the qualifications, limitations, and restrictions of the preferred stock of each series. To the extent the certificate of incorporation does not set forth the rights and limitations, they will be fixed by the certificate of designation relating to the series. A prospectus supplement relating to each series will specify the terms of the preferred stock as follows:

      The prospectus supplement may, in a manner not inconsistent with the provisions of the certificate of incorporation:

      Holders of the preferred stock of any series shall be entitled to receive, when, as and if declared by the board of directors, preferential dividends in cash at the annual rate, if any, fixed for the series. Their entitlement will be subject to any limitations specified in the certificate of incorporation and in the certificate of designation providing for the issuance of a particular series of preferred stock. The certificate of designation providing for the issuance of preferred stock of the series may specify the date on which the preferential dividends are payable. The preferential dividends shall further be payable to stockholders of record on a date which precedes each dividend payment date which the board of directors has fixed in advance of each particular dividend.

      Each share of preferred stock shall rank on a parity with each other share of preferred stock, irrespective of series, with respect to preferential dividends accrued on the shares of the series. We will not declare or pay any dividend nor will we set apart a dividend for payment for the preferred stock of any series unless at the same time we declare, pay, or set apart a dividend in like proportion to the dividends accrued upon the preferred stock of each other series. This does not, however, prevent us from authorizing or issuing one or more series of preferred stock bearing dividends subject to contingencies as to the existence or amount of our earnings during one or more fiscal periods, or as to other events, to which dividends on other series of preferred stock are not subject.

      So long as any shares of preferred stock remain outstanding, we will not, unless all dividends accrued on outstanding shares of preferred stock for all past dividend periods shall have been paid or declared and a sum sufficient for the payment of the dividends set apart:

      As a holding company, our ability to pay dividends on the preferred stock will depend upon the payment of dividends, interest, or other charges by our subsidiaries to us. Debt instruments of certain of our subsidiaries may limit the amount of payments to us, which could affect the amount of funds available to us to pay dividends on the preferred stock.

      The registrar, transfer agent, and dividend disbursing agent for the preferred stock will be named in the applicable prospectus supplement.

      With the approval of our board of directors, we may redeem all or any part of the preferred stock of any series that by its terms is redeemable. Redemption will take place at the time or times and on the terms and conditions fixed for the series. We must duly give notice in the manner provided in the certificate of designation providing for the series. We must pay for preferred stock in cash the sum fixed for the series, together, in each case, with an amount equal to accrued and unpaid dividends on the series of preferred stock.

The certificate of designation providing for a series of preferred stock that is subject to redemption may provide, upon the two conditions discussed below, that the shares will no longer be deemed outstanding, and all rights with respect to the shares will cease, including the accrual of further dividends, other than the right to receive the redemption price of the shares without interest, when:

      Redemption will terminate the right of holders of the preferred stock to accrual of further dividends. Redemption will not, however, terminate the right of holders of the shares redeemed to receive the redemption price for the shares without interest.

      The preferred stock will have no right or power to vote on any question or in any proceeding or to be represented at or to receive notice of any meeting of stockholders, except as:

      On any matters on which the holders of the preferred stock or any series thereof shall be entitled to vote separately as a class or series, they shall be entitled to one vote for each share held.

      So long as any shares of preferred stock are outstanding, we must not, during the continuance of any default in the payment of dividends on the preferred stock, redeem or otherwise acquire for value any shares of the preferred stock or of any other stock ranking on a parity with the preferred stock concerning dividends or distribution of assets on liquidation. Holders of a majority of the number of shares of preferred stock outstanding at the time may, however, permit such a redemption by giving their consent in person or by proxy, either in writing or by vote at any annual meeting or any special meeting called for the purpose.

      In the event of any voluntary or involuntary liquidation, dissolution, or winding up of the affairs of Williams, the holders of the preferred stock of the respective series are entitled to be paid in full the following amounts:

      We must have made this payment in full to the holders of the preferred stock before we may make any distribution or payment to the holders of any class of stock ranking junior to the preferred stock as to dividends or distribution of assets on liquidation. After we have made this payment in full to the holders of the preferred stock, our remaining assets and funds will be distributed among the holders of our stock ranking junior to the preferred stock according to their rights. If our assets available for distribution to holders of preferred stock are sufficient to make the payment required to be made in full, these assets will be distributed to the holders of shares of preferred stock proportionately to the amounts payable upon each share of preferred stock.

Common Stock

      As of the date of this prospectus, we are authorized to issue up to 960,000,000 shares of common stock, par value $1.00 per share. As of May 15, 2006, we had 616,684,636 issued and outstanding shares of common

stock. In addition, as of May 15, 2006, 23,688,849 shares of common stock were subject to options or deferred rights outstanding under various stock and compensation incentive plans. The outstanding shares of common stock are fully paid and nonassessable. The holders of common stock are not entitled to preemptive or redemption rights. Shares of common stock are not convertible into shares of any other class of capital stock. Computershare Limited, formerly EquiServe Trust Company, N.A. (“Computershare”), is the transfer agent and registrar for our common stock. Our common stock is listed on the New York Stock Exchange under the ticker symbol “WMB.”

      The holders of our common stock are entitled to receive dividends when, as, and if declared by our board of directors, out of funds legally available for their payment subject to the rights of holders of any outstanding preferred stock.

      The holders of our common stock are entitled to one vote per share on all matters submitted to a vote of stockholders.

      In the event of our voluntary or involuntary liquidation, dissolution, or winding up of the affairs of Williams, the holders of our common stock will be entitled to share equally in any assets available for distribution after the payment in full of all debts and distributions and after the holders of all series of outstanding preferred stock have received their liquidation preferences in full.

Preferred Stock Purchase Rights

      On September 21, 2004, we entered into an amended and restated rights agreement with Computershare, as rights agent. The amended and restated rights agreement provides for a one-third preferred stock purchase right for each outstanding share of our common stock (subject to adjustment for stock splits, stock dividends and recapitalizations with respect to our common stock). The rights trade automatically with shares of common stock and become exercisable only under the circumstances described below. The rights are designed to protect the interests of us and our stockholders against coercive takeover tactics. The purpose of the rights is to encourage potential acquirers to negotiate with our board prior to attempting a takeover and to provide the board with leverage in negotiating on behalf of all stockholders the terms of any proposed takeover. The rights may have anti-takeover effects. The rights should not, however, interfere with a merger or other business combination approved by our board.

      Until a right is exercised, the right does not entitle the holder to additional rights as a stockholder, including, without limitation, the right to vote or to receive dividends. Upon becoming exercisable, each right entitles its holder to purchase from us one two-hundredth of a share of Series A Junior Participating Preferred Stock at an exercise or purchase price of $50.00 per right, subject to adjustment. Each share of Series A Junior Participating Preferred Stock entitles the holder to receive quarterly dividends payable in cash of an amount per share equal to:

      The dividends on the Series A Junior Participating Preferred Stock are cumulative. Holders of Series A Junior Participating Preferred Stock have voting rights entitling them to 1,200 votes per share on all matters submitted to a vote of our stockholders.

      In general, the rights will not be exercisable until the distribution date, which is the earlier of (a) the date of the first Section 11(a)(ii) Event (as defined below) or the date of the first Section 13 Event (as defined below) and (b) the close of business on the 10th business day (or such later date as our board shall determine) after the commencement of a tender or exchange offer for 15% or more of our outstanding common stock. A person or group acquiring at least 15% of our common stock is referred to as an “acquiring person” below.

      In the event that a person or group acquires beneficial ownership of 15% or more of our outstanding common stock as described in Section 11(a)(ii) of the amended and restated rights agreement (a “Section 11(a)(ii) Event”) and the expiration date has not occurred prior to the tenth business day after a Section 11(a)(ii) Event, each holder of a right will have the right to exercise and receive common stock having a value equal to two times the exercise price of the right. The exercise price is the purchase price times the number of shares of common stock associated with each right. Any rights that are at any time beneficially owned by an acquiring person will be null and void and any holder of such right will be unable to exercise or transfer the right.

      In the event that at any time prior to the earlier of the redemption date or the expiration date as defined in the amended and restated rights agreement, a Section 13 Event as described in Section 13 of the amended and restated rights agreement occurs, each right becomes exercisable and each right will entitle its holder to receive common stock of the principal party having a value equal to two times the exercise price of the right. A Section 13 Event is where we either (a) engage in a merger or other business combination in which we are not the surviving corporation, (b) engage in a merger or other business combination in which we are the surviving corporation but all or a part of our common stock is changed or exchanged, or (c) sell or transfer 50% or more of our assets, cash flow or earning power.

      The rights will expire at the close of business on September 21, 2014, unless redeemed before that time. At any time prior to the earlier of (a) a Section 11(a)(ii) Event, (b) the date of the first Section 13 Event, and (c) September 21, 2014, our board may redeem the rights in whole, but not in part, at a price of $0.01 per right. Prior to the date of the first Section 11(a)(ii) Event or the date of the first Section 13 Event, we may amend the amended and restated rights agreement in any respect without the approval of the rights holders. However, after the date of the first Section 11(a)(ii) Event or the date of the first Section 13 Event, the amended and restated rights agreement may not be amended in any way that would adversely affect the holders of rights (other than any acquiring person or a principal party). The Series A Junior Participating Preferred Stock ranks junior to all other existing and future series of our preferred stock as to the payment of dividends and the distribution of assets unless the terms of the series specify otherwise. Holders should refer to the applicable provisions of the amended and restated rights agreement, which we filed with the SEC as Exhibit 4.1 to our Current Report on Form 8-K filed September 21, 2004.

Certain Certificate of Incorporation Provisions

      We currently have the following provisions in our charter or bylaws that could be considered to be “anti-takeover” provisions:

      We are a Delaware corporation and are subject to Section 203 of the Delaware General Corporation Law. In general, Section 203 prevents an interested stockholder, which is defined generally as a person owning 15% or more of our outstanding voting stock, from engaging in a business combination with us for three years following the date that person became an interested stockholder unless:

      A business combination includes mergers, asset sales and other transactions resulting in a financial benefit to the interested stockholder.

DESCRIPTION OF PURCHASE CONTRACTS

      We may issue purchase contracts for the purchase or sale of:

      Each purchase contract will entitle the holder thereof to purchase or sell, and obligate us to sell or purchase, on specified dates, such securities, currencies or commodities at a specified purchase price, which may be based on a formula, all as set forth in the applicable prospectus supplement. We may, however, satisfy our obligations, if any, with respect to any purchase contract by delivering the cash value of such purchase contract or the cash value of the property otherwise deliverable or, in the case of purchase contracts on underlying currencies, by delivering the underlying currencies, as set forth in the applicable prospectus supplement. The applicable prospectus supplement will also specify the methods by which the holders may purchase or sell such securities, currencies or commodities and any acceleration, cancellation or termination provisions or other provisions relating to the settlement of a purchase contract.

      The purchase contracts may require us to make periodic payments to the holders thereof or vice versa, which payments may be deferred to the extent set forth in the applicable prospectus supplement, and those payments may be unsecured or prefunded on some basis. The purchase contracts may require the holders thereof to secure their obligations in a specified manner to be described in the applicable prospectus supplement. Alternatively, purchase contracts may require holders to satisfy their obligations thereunder when the purchase contracts are issued. Our obligation to settle such pre-paid purchase contracts on the relevant settlement date may constitute indebtedness. Accordingly, pre-paid purchase contracts will be issued under the indenture, a form of which is filed as an exhibit to the registration statement of which this prospectus is a part.

DESCRIPTION OF WARRANTS

      We may issue warrants to purchase our debt or equity securities or securities of third parties or other rights, including rights to receive payment in cash or securities based on the value, rate or price of one or more specified commodities, currencies, securities or indices, or any combination of the foregoing. Warrants may be issued independently or together with any other securities and may be attached to, or separate from, such securities. Each series of warrants will be issued under a separate warrant agreement to be entered into between us and a warrant agent. The terms of any warrants to be issued and a description of the material provisions of the applicable warrant agreement will be set forth in the applicable prospectus supplement.

      The applicable prospectus supplement will describe the following terms of any warrants in respect of which this prospectus is being delivered:

DESCRIPTION OF UNITS

      As specified in the applicable prospectus supplement, we may issue units consisting of one or more purchase contracts, warrants, debt securities, shares of preferred stock, shares of common stock or any combination of such securities. The applicable prospectus supplement will describe:

SELLING SECURITYHOLDERS

      Information about selling securityholders, where applicable, will be set forth in a prospectus supplement, in a post-effective amendment, or in filings we make with the SEC under the Exchange Act that are incorporated by reference.

LEGAL MATTERS

      Certain legal matters will be passed upon for us by Gibson, Dunn & Crutcher LLP. Any agents or underwriters will be represented by their own legal counsel named in the applicable prospectus supplement.

EXPERTS

      The consolidated financial statements of Williams appearing in the 2005 Form 10-K (including the schedule appearing therein), and Williams’ management’s assessment of the effectiveness of internal control over financial reporting as of December 31, 2005, included therein, have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their reports thereon, included therein, and incorporated herein by reference. Such consolidated financial statements and management’s assessment are incorporated herein by reference in reliance upon such reports given on the authority of such firm as experts in accounting and auditing.

      Approximately 99% of Williams’ year-end 2005 U.S. proved reserves estimates included in the 2005 Form 10-K were either audited by Netherland, Sewell & Associates, Inc., or, in the case of reserves estimates related to properties underlying the Williams Coal Seam Gas Royalty Trust, were prepared by Miller and Lents, LTD.

PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

      The following table sets forth the estimated fees and expenses payable by us in connection with the offering of the securities being registered, other than discounts and commissions.

      Williams, a Delaware corporation, is empowered by Section 145 of the General Corporation Law of the State of Delaware, subject to the procedures and limitations stated therein, to indemnify any person against expenses (including attorneys’ fees), judgments, fines, and amounts paid in settlement actually and reasonably incurred by them in connection with any threatened, pending, or completed action, suit, or proceeding in which such person is made party by reason of their being or having been a director, officer, employee, or agent of Williams. The statute provides that indemnification pursuant to its provisions is not exclusive of other rights of indemnification to which a person may be entitled under any bylaw, agreement, vote of stockholders or disinterested directors, or otherwise. Our By-laws provide for indemnification by us of our directors and officers to the fullest extent permitted by the General Corporation Law of the State of Delaware. In addition, we have entered into indemnity agreements with its directors and certain officers providing for, among other things, the indemnification of and the advancing of expenses to such individuals to the fullest extent permitted by law, and to the extent insurance is maintained, for the continued coverage of such individuals.

      Policies of insurance are maintained by us under which our directors and officers are insured, within the limits and subject to the limitations of the policies, against certain expenses in connection with the defense of actions, suits, or proceedings, and certain liabilities which might be imposed as a result of such actions, suits or proceedings, to which they are parties by reason of being or having been such directors or officers.

      A list of exhibits included as part of this registration statement is set forth in the Exhibit Index, which immediately precedes such exhibits and is incorporated herein by reference.

      The undersigned registrant hereby undertakes:

      To file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement:

provided, however, that paragraphs (i), (ii) and (iii) do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the SEC by the registrant pursuant to Section 13 or Section 15(d) of the Exchange Act that are incorporated by reference in the registration statement, or is contained in a form of prospectus filed pursuant to Rule 424(b) that is part of the registration statement.

      That, for the purpose of determining any liability under the Securities Act, each post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

      To remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering.

      That, for the purpose of determining liability under the Securities Act to any purchaser:

      That, for the purpose of determining liability of the registrant under the Securities Act to any purchaser in the initial distribution of the securities, the undersigned registrant undertakes that in a primary offering of securities of the undersigned registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, the undersigned registrant will be a seller to the purchaser and will be considered to offer or sell such securities to such purchaser:

      That, for purposes of determining any liability under the Securities Act, each filing of the registrant’s annual report pursuant to Section 13(a) or Section 15(d) of the Exchange Act (and, where applicable, each filing of an employee benefit plan’s annual report pursuant to Section 15(d) of the Exchange Act) that is incorporated by reference in the registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

      To file an application for the purpose of determining the eligibility of the trustee to act under subsection (a) of Section 310 of the Trust Indenture Act in accordance with the rules and regulations prescribed by the SEC under Section 305(b)(2) of the Trust Indenture Act.

      Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers and controlling persons of the registrant pursuant to the foregoing provisions, or otherwise, the registrant has been advised that in the opinion of the SEC such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the registrant will, unless in the opinion of counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

SIGNATURES

      Pursuant to the requirements of the Securities Act of 1933, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the city of Tulsa, state of Oklahoma on May 19, 2006.

      Pursuant to the requirements of the Securities Act of 1933, this registration statement has been signed below by the following persons in the capacities and on the dates indicated.

EXHIBIT INDEX