THE TRANSFER OF THIS AGREEMENT IS SUBJECT TO CERTAIN PROVISIONS CONTAINED HEREIN AND TO RESALE RESTRICTIONS UNDER THE SECURITIES ACT OF 1933, AS AMENDED

Exhibit 99.1

EXECUTION COPY

THE TRANSFER OF THIS AGREEMENT IS SUBJECT TO

CERTAIN PROVISIONS CONTAINED HEREIN AND TO

RESALE RESTRICTIONS UNDER THE

SECURITIES ACT OF 1933, AS AMENDED

STOCK OPTION AGREEMENT (this “Agreement”), dated May 24, 2006, between Regions Financial Corporation, a Delaware corporation (“Issuer”), and AmSouth Bancorporation, a Delaware corporation (“Grantee”).

W I T N E S S E T H:

WHEREAS, Grantee and Issuer have entered into an Agreement and Plan of Merger of even date herewith (the “Merger Agreement”), which agreement has been executed and delivered by the parties hereto simultaneously with this Agreement;

WHEREAS, as a condition to Grantee’s entering into the Merger Agreement and in consideration therefor, Issuer has agreed to grant Grantee the Option (as hereinafter defined); and

WHEREAS, in connection with entering into the Merger Agreement, the Grantee has issued the Issuer an option (the “Reciprocal Option”) pursuant to a Stock Option Agreement in the form attached to the Merger Agreement.

NOW, THEREFORE, in consideration of the foregoing and the mutual covenants and agreements set forth herein and in the Merger Agreement, the parties hereto agree as follows:

1. (a) Issuer hereby grants to Grantee an unconditional, irrevocable option (the “Option”) to purchase, subject to the terms hereof, up to 90,767,194 fully paid and nonassessable shares of Issuer’s Common Stock, par value $0.01 per share (“Common Stock”), at a price of the lesser (i) $35.53 per share and (ii) the closing sale price of the Common Stock on the NYSE Composite Transaction Tape on the trading day immediately preceding the exercise date as reported by The Wall Street Journal or, if not reported therein, in another authoritative source (the “Option Price”); provided, however, that in no event shall the number of shares of Common Stock for which this Option is exercisable exceed 19.9% of the Issuer’s issued and outstanding shares of Common Stock without giving effect to any shares subject to or issued pursuant to the Option. The number of shares of Common Stock that may be received upon the exercise of the Option and the Option Price are subject to adjustment as herein set forth. If Issuer adopts a shareholder protection rights plan or similar agreement, Issuer shall make proper provision so that each share of Common Stock issued upon exercise of the Option shall be accompanied by the applicable number of rights under such agreement.

(b) In the event that any additional shares of Common Stock are either (i) issued or otherwise become outstanding after the date of this Agreement (other than pursuant to this Agreement) or (ii) redeemed, repurchased, retired or otherwise cease to be outstanding after the date of this Agreement, the number of shares of Common Stock subject to the Option shall be increased or decreased, as appropriate, so that, after such issuance, such number equals 19.9% of the number of shares of Common Stock then issued and outstanding without giving effect to any shares subject or issued pursuant to the Option. Nothing contained in this Section 1(b) or elsewhere in this Agreement shall be deemed to authorize Issuer or Grantee to breach any provision of the Merger Agreement.

2. (a) The Holder (as hereinafter defined) may exercise the Option, in whole or part, and from time to time, if, but only if, both an Initial Triggering Event (as hereinafter defined) and a Subsequent Triggering Event (as hereinafter defined) shall have occurred prior to the occurrence of an Exercise Termination Event (as hereinafter defined), provided that the Holder shall have sent the written notice of such exercise (as provided in subsection (g) of this Section 2) within 180 days following such Subsequent Triggering Event.

(b) Each of the following shall be an “Exercise Termination Event”: (i) the Effective Time (as defined in the Merger Agreement) of the Merger; (ii) termination of the Merger Agreement in accordance with the provisions thereof (other than a termination by Grantee pursuant to Section 6.1(e) or pursuant to Section 6.1(b) (unless the breach by Issuer giving rise to such right of termination pursuant to Section 6.1(b) is non-volitional)) if such termination occurs prior to the occurrence of an Initial Triggering Event; and (iii) the passage of 18 months after termination of the Merger Agreement if such termination follows the occurrence of an Initial Triggering Event or is a termination by Grantee pursuant to Section 6.1(e) or pursuant to Section 6.1(b) (unless the breach by Issuer giving rise to such right of termination pursuant to Section 6.1(b) is non-volitional) of the Merger Agreement.

(d) The term “Initial Triggering Event” shall mean any of the following events or transactions occurring on or after the date hereof:

(i) Issuer or any of its Subsidiaries (each an “Issuer Subsidiary”), without having received Grantee’s prior written consent, shall have entered into an agreement to engage in an Acquisition Transaction (as hereinafter defined) with any person (the term “person” for purposes of this Agreement having the meaning assigned thereto in Sections 3(a)(9) and 13(d)(3) of the Securities Exchange Act of 1934, as amended (the “1934 Act”), and the rules and regulations thereunder) other than Grantee or any of its Subsidiaries (each a “Grantee Subsidiary”) or the Board of Directors of Issuer shall have recommended that the stockholders of Issuer approve or accept any Acquisition Transaction with any person other than Grantee or a Subsidiary of Grantee. For purposes of this Agreement, “Acquisition Transaction” shall mean (w) a merger, consolidation or share exchange, or any similar transaction, involving Issuer or any Significant Subsidiary (as defined in Rule 1-02 of Regulation S-X promulgated by the

Securities and Exchange Commission (the “SEC”)) of Issuer, (x) a purchase, lease or other acquisition or assumption of all or a substantial portion of the assets or deposits of Issuer or any Significant Subsidiary of Issuer, (y) a purchase or other acquisition (including by way of merger, consolidation, share exchange or otherwise) of securities representing 10% or more of the voting power of Issuer, or (z) any substantially similar transaction; provided, however, that in no event shall any merger, consolidation, purchase or similar transaction that is not entered into in violation of the terms of the Merger Agreement and involves only the Issuer and one or more of its wholly-owned Subsidiaries or only any two or more of such wholly-owned Subsidiaries, be deemed to be an Acquisition Transaction;

(ii) Issuer or any Issuer Subsidiary, without having received Grantee’s prior written consent, shall have authorized, recommended, proposed or publicly announced its intention to authorize, recommend or propose, to engage in an Acquisition Transaction with any person other than Grantee or a Grantee Subsidiary, or the Board of Directors of Issuer shall have publicly withdrawn or modified, or publicly announced its intention to withdraw or modify, in any manner adverse to Grantee, its recommendation that the stockholders of Issuer approve the transactions contemplated by the Merger Agreement;

(iii) Any person other than Grantee, any Grantee Subsidiary or any Issuer Subsidiary acting in a fiduciary capacity in the ordinary course of its business shall have acquired beneficial ownership or the right to acquire beneficial ownership of 10% or more of the outstanding shares of Common Stock (the term “beneficial ownership” for purposes of this Agreement having the meaning assigned thereto in Section 13(d) of the 1934 Act, and the rules and regulations thereunder);

(iv) Any person other than Grantee or any Grantee Subsidiary shall have made a bona fide proposal to Issuer or its stockholders that is public or becomes the subject of public disclosure to engage in an Acquisition Transaction;

(v) After the receipt by Issuer or its stockholders of any bona fide inquiry or proposal (or the bona fide indication of any intention to propose) from a third party to engage in an Acquisition Transaction, Issuer shall have breached any covenant or obligation contained in the Merger Agreement and such breach (x) would entitle Grantee to terminate the Merger Agreement and (y) shall not have been cured prior to the Notice Date (as defined below); or

(vi) Any person other than Grantee or any Grantee Subsidiary, other than in connection with a transaction to which Grantee has given its prior written consent, shall have filed an application or notice with the Federal Reserve Board, or other federal or state bank regulatory authority, which application or notice has been accepted for processing, for approval to engage in an Acquisition Transaction.

(e) The term “Subsequent Triggering Event” shall mean either of the following events or transactions occurring on or after the date hereof:

(i) The acquisition by any person of beneficial ownership of 20% or more of the then outstanding Common Stock; or

(ii) The occurrence of the Initial Triggering Event described in paragraph (i) of subsection (d) of this Section 2, except that the percentage referred to in clause (y) shall be 20%.

(f) Issuer shall notify Grantee promptly in writing of the occurrence of any Initial Triggering Event or Subsequent Triggering Event of which it has knowledge, it being understood that the giving of such notice by Issuer shall not be a condition to the right of the Holder to exercise the Option.

(g) In the event the Holder is entitled to and wishes to exercise the Option, it shall send to Issuer a written notice (the date of which being herein referred to as the “Notice Date”) specifying (i) the total number of shares it will purchase pursuant to such exercise and (ii) a place and date not earlier than three business days nor later than 60 business days from the Notice Date for the closing of such purchase (the “Closing Date”); provided that if prior notification to or approval of the Federal Reserve Board or any other regulatory agency is required in connection with such purchase, the Holder shall as soon as reasonably practicable file the required notice or application for approval and shall expeditiously process the same, and the period of time that otherwise would run pursuant to this sentence shall run instead from the date on which any required notification periods have expired or been terminated or such approvals have been obtained and any requisite waiting period or periods shall have passed. Any exercise of the Option shall be deemed to occur on the Notice Date relating thereto.

(h) At the closing referred to in subsection (g) of this Section 2, the Holder shall pay to Issuer the aggregate purchase price for the shares of Common Stock purchased pursuant to the exercise of the Option in immediately available funds by wire transfer to a bank account designated by Issuer, provided that failure or refusal of Issuer to designate such a bank account shall not preclude the Holder from exercising the Option.

(i) At such closing, simultaneously with the delivery of immediately available funds as provided in subsection (h) of this Section 2, Issuer shall deliver to the Holder a certificate or certificates representing the number of shares of Common Stock purchased by the Holder and, if the Option should be exercised in part only, a new Option evidencing the rights of the Holder thereof to purchase the balance of the shares purchasable hereunder, and the Holder shall deliver to Issuer this Agreement and a letter agreeing that the Holder will not offer to sell or otherwise dispose of such shares in violation of applicable law or the provisions of this Agreement.

(j) Certificates for Common Stock delivered at a closing hereunder may be endorsed with a restrictive legend that shall read substantially as follows:

“The transfer of the shares represented by this certificate is subject to certain provisions of an agreement between the registered holder hereof and Issuer and to resale restrictions arising under the Securities Act of 1933, as amended. A copy

of such agreement is on file at the principal office of Issuer and will be provided to the holder hereof without charge upon receipt by Issuer of a written request therefor.”

It is understood and agreed that: (i) the reference to the resale restrictions of the Securities Act of 1933, as amended (the “1933 Act”), in the above legend shall be removed by delivery of substitute certificate(s) without such reference if the Holder shall have delivered to Issuer a copy of a letter from the staff of the SEC, or an opinion of counsel, in form and substance reasonably satisfactory to Issuer, to the effect that such legend is not required for purposes of the 1933 Act; (ii) the reference to the provisions of this Agreement in the above legend shall be removed by delivery of substitute certificate(s) without such reference if the shares have been sold or transferred in compliance with the provisions of this Agreement and under circumstances that do not require the retention of such reference; and (iii) the legend shall be removed in its entirety if the conditions in the preceding clauses (i) and (ii) are both satisfied. In addition, such certificates shall bear any other legend as may be required by law.

(k) Upon the giving by the Holder to Issuer of the written notice of exercise of the Option provided for under subsection (g) of this Section 2 and the tender of the applicable purchase price in immediately available funds, the Holder shall be deemed to be the holder of record of the shares of Common Stock issuable upon such exercise, notwithstanding that the stock transfer books of Issuer shall then be closed or that certificates representing such shares of Common Stock shall not then be actually delivered to the Holder. Issuer shall pay all expenses, and any and all United States federal, state and local taxes and other charges that may be payable in connection with the preparation, issuance and delivery of stock certificates under this Section 2 in the name of the Holder or its assignee, transferee or designee.

3. Issuer agrees: (i) that it shall at all times maintain, free from preemptive rights, sufficient authorized but unissued shares of Common Stock so that the Option may be exercised without additional authorization of Common Stock after giving effect to all other options, warrants, convertible securities and other rights to purchase Common Stock; (ii) that it will not, by charter amendment or through reorganization, consolidation, merger, dissolution or sale of assets, or by any other voluntary act, avoid or seek to avoid the observance or performance of any of the covenants, stipulations or conditions to be observed or performed hereunder by Issuer; (iii) promptly to take all action as may from time to time be required (including (x) complying with all premerger notification, reporting and waiting period requirements specified in 15 U.S.C. § 18a and regulations promulgated thereunder and (y) in the event, under the Bank Holding Company Act of 1956, as amended (the “BHCA”), or the Change in Bank Control Act of 1978, as amended, or any state banking law, prior approval of or notice to the Federal Reserve Board or to any state or other regulatory authority is necessary before the Option may be exercised, cooperating fully with the Holder in preparing such applications or notices and providing such information to the Federal Reserve Board or such other regulatory authority as they may require) in order to permit the Holder to exercise the Option and Issuer duly and effectively to issue shares of Common Stock pursuant hereto; and (iv) promptly to take all action provided herein to protect the rights of the Holder against dilution.

4. This Agreement (and the Option granted hereby) are exchangeable, without expense, at the option of the Holder, upon presentation and surrender of this Agreement at the principal office of Issuer, for other Agreements providing for Options of different denominations entitling the holder thereof to purchase, on the same terms and subject to the same conditions as are set forth herein, in the aggregate the same number of shares of Common Stock purchasable hereunder. The terms “Agreement” and “Option” as used herein include any Stock Option Agreements and related Options for which this Agreement (and the Option granted hereby) may be exchanged. Upon receipt by Issuer of evidence reasonably satisfactory to it of the loss, theft, destruction or mutilation of this Agreement, and (in the case of loss, theft or destruction) of reasonably satisfactory indemnification, and upon surrender and cancellation of this Agreement, if mutilated, Issuer will execute and deliver a new Agreement of like tenor and date. Any such new Agreement executed and delivered shall constitute an additional contractual obligation on the part of Issuer, whether or not the Agreement so lost, stolen, destroyed or mutilated shall at any time be enforceable by anyone.

5. In addition to the adjustment in the number of shares of Common Stock that are purchasable upon exercise of the Option pursuant to Section 1 of this Agreement, the number of shares of Common Stock purchasable upon the exercise of the Option and the Option Price shall be subject to adjustment from time to time as provided in this Section 5. In the event of any change in, or distributions in respect of, the Common Stock by reason of stock dividends, split-ups, mergers, recapitalizations, combinations, subdivisions, conversions, exchanges of shares, distributions on or in respect of the Common Stock that would cause an adjustment to the number of shares of Regions Common Stock that each share of AmSouth Common Stock shall represent the right to receive upon conversion under the terms of the Merger Agreement, or the like, the type and number of shares of Common Stock purchasable upon exercise hereof and the Option Price shall be appropriately adjusted in such manner as shall fully preserve the economic benefits provided hereunder and proper provision shall be made in any agreement governing any such transaction to provide for such proper adjustment and the full satisfaction of the Issuer’s obligations hereunder.

6. Upon the occurrence of a Subsequent Triggering Event that occurs prior to an Exercise Termination Event, Issuer shall, at the request of Grantee delivered within 180 days of such Subsequent Triggering Event (whether on its own behalf or on behalf of any subsequent holder of this Option (or part thereof) or any of the shares of Common Stock issued pursuant hereto), promptly prepare, file and keep current a shelf registration statement under the 1933 Act covering this Option and any shares issued and issuable pursuant to this Option and shall use its reasonable best efforts to cause such registration statement to become effective and remain current in order to permit the sale or other disposition of this Option and any shares of Common Stock issued upon total or partial exercise of this Option (“Option Shares”) in accordance with any plan of disposition requested by Grantee. Issuer will use its reasonable best efforts to cause such registration statement first to become effective and then to remain effective for such period not in excess of 180 days from the day such registration statement first becomes effective or such shorter time as may be reasonably necessary to effect such sales or other dispositions. Grantee shall have the right to demand two such registrations. The Issuer shall bear the costs of such registrations (including, but not limited to, Issuer’s attorneys’ fees, printing costs and filing fees,

except for the fees and disbursements of Grantee’s counsel related thereto). The foregoing notwithstanding, if, at the time of any request by Grantee for registration of the Option or Option Shares as provided above, Issuer is in registration with respect to an underwritten public offering of shares of Common Stock, and if in the good faith judgment of the managing underwriter or managing underwriters, or, if none, the sole underwriter or underwriters, of such offering the inclusion of the Holder’s Option or Option Shares would interfere with the successful marketing of the shares of Common Stock offered by Issuer, the number of Option Shares otherwise to be covered in the registration statement contemplated hereby may be reduced; provided, however, that after any such required reduction the number of Option Shares to be included in such offering for the account of the Holder shall constitute at least 25% of the total number of shares to be sold by the Holder and Issuer in the aggregate; and provided further, however, that if such reduction occurs, then the Issuer shall file a registration statement for the balance as promptly as practicable and no reduction shall thereafter occur. Each such Holder shall provide all information reasonably requested by Issuer for inclusion in any registration statement to be filed hereunder. If requested by any such Holder in connection with such registration, Issuer shall become a party to any underwriting agreement relating to the sale of such shares, but only to the extent of obligating itself in respect of representations, warranties, indemnities and other agreements customarily included in secondary offering underwriting agreements for the Issuer. Upon receiving any request under this Section 6 from any Holder, Issuer agrees to send a copy thereof to any other person known to Issuer to be entitled to registration rights under this Section 6, in each case by promptly mailing the same, postage prepaid, to the address of record of the persons entitled to receive such copies. Notwithstanding anything to the contrary contained herein, in no event shall Issuer be obligated to effect more than two registrations pursuant to this Section 6 by reason of the fact that there shall be more than one Grantee as a result of any assignment or division of this Agreement.

7. (a) In the event of a Repurchase Event (as defined below), (i) following a request of the Holder, delivered prior to an Exercise Termination Event, Issuer (or any successor thereto) shall repurchase the Option from the Holder immediately prior to the Repurchase Event (or, as requested by the Holder, after the Repurchase Event) at a price (the “Option Repurchase Price”) equal to the product of the number of shares for which this Option may then be exercised multiplied by the amount by which (A) the Market/Offer Price (as defined below) exceeds (B) the Option Price, and (ii) at the request of the owner of Option Shares from time to time (the “Owner”), delivered prior to an Exercise Termination Event and within 90 days of the occurrence of a Repurchase Event, Issuer (or any successor thereto) shall repurchase immediately prior to the Repurchase Event (or, as requested by the Owner, after the Repurchase Event) such number of the Option Shares from the Owner as the Owner shall designate at a price (the “Option Share Repurchase Price”) equal to the Market/Offer Price multiplied by the number of Option Shares so designated. The term “Market/Offer Price” shall mean the highest of (i) the price per share of Common Stock at which a tender offer or exchange offer therefor has been made, (ii) the price per share of Common Stock to be paid by any third party pursuant to an agreement with Issuer, (iii) the highest closing price for shares of Common Stock within the six-month period immediately preceding the date the Holder gives notice of the required repurchase of this Option or the Owner gives notice of the required repurchase of Option Shares, as the case may be, and (iv) in the event of a sale of Issuer’s assets, the sum of the price paid in such sale for

such assets and the current market value of the remaining assets of Issuer as determined by a nationally recognized investment banking firm selected by the Holder or the Owner, as the case may be, and reasonably acceptable to the Issuer, divided by the number of shares of Common Stock of Issuer outstanding at the time of such sale. In determining the Market/Offer Price, the value of consideration other than cash shall be determined by a nationally recognized investment banking firm selected by the Holder or Owner, as the case may be, and reasonably acceptable to the Issuer.

(b) The Holder and the Owner, as the case may be, may exercise its right to require Issuer to repurchase the Option and any Option Shares pursuant to this Section 7 by surrendering for such purpose to Issuer, at its principal office, this Agreement or certificates for Option Shares, as applicable, accompanied by a written notice or notices stating that the Holder or the Owner, as the case may be, elects to require Issuer to repurchase this Option and/or the Option Shares in accordance with the provisions of this Section 7. Within five business days after the surrender of the Option and/or certificates representing Option Shares and the receipt of such notice or notices relating thereto Issuer shall deliver or cause to be delivered to the Holder the Option Repurchase Price and/or to the Owner the Option Share Repurchase Price therefor or the portion thereof, if any, that Issuer is not then prohibited under applicable law and regulation from so delivering.

(c) To the extent that Issuer is prohibited under applicable law or regulation from repurchasing the Option and/or the Option Shares in full, Issuer shall immediately so notify the Holder and/or the Owner and thereafter deliver or cause to be delivered, from time to time, to the Holder and/or the Owner, as appropriate, the portion of the Option Repurchase Price and the Option Share Repurchase Price, respectively, that it is no longer prohibited from delivering, within five business days after the date on which Issuer is no longer so prohibited; provided, however, that if Issuer at any time after delivery of a notice of repurchase pursuant to paragraph (b) of this Section 7 is prohibited under applicable law or regulation from delivering to the Holder and/or the Owner, as appropriate, the Option Repurchase Price and the Option Share Repurchase Price, respectively, in full (and Issuer hereby undertakes to use its reasonable best efforts to obtain all required regulatory and legal approvals and to file any required notices, in each case as promptly as practicable in order to accomplish such repurchase), the Holder or Owner may revoke its notice of repurchase of the Option or the Option Shares either in whole or to the extent of the prohibition, whereupon, in the latter case, Issuer shall promptly (i) deliver to the Holder and/or the Owner, as appropriate, that portion of the Option Repurchase Price or the Option Share Repurchase Price that Issuer is not prohibited from delivering; and (ii) deliver, as appropriate, either (A) to the Holder, a new Stock Option Agreement evidencing the right of the Holder to purchase that number of shares of Common Stock obtained by multiplying the number of shares of Common Stock for which the surrendered Stock Option Agreement was exercisable at the time of delivery of the notice of repurchase by a fraction, the numerator of which is the Option Repurchase Price less the portion thereof theretofore delivered to the Holder and the denominator of which is the Option Repurchase Price, or (B) to the Owner, a certificate for the Option Shares it is then so prohibited from repurchasing.

(d) For purposes of this Section 7, a “Repurchase Event” shall be deemed to have occurred (i) upon the consummation of an Acquisition Transaction with respect to Issuer (and not solely involving Issuer and/or one or more subsidiaries of Issuer) (except that the percentage referred to in clause (y) of the definition thereof shall be 50%) or (ii) upon the acquisition by any person of beneficial ownership of 50% or more of the then outstanding shares of Common Stock.

8. (a) In the event that, prior to an Exercise Termination Event, Issuer shall enter into an agreement (i) to consolidate with or merge into any person, other than Grantee or one of its Subsidiaries, and shall not be the continuing or surviving corporation of such consolidation or merger, (ii) to permit any person, other than Grantee or one of its Subsidiaries, to merge into Issuer and Issuer shall be the continuing or surviving corporation, but, in connection with such merger, the then outstanding shares of Common Stock shall be changed into or exchanged for stock or other securities of any other person or cash or any other property or the then outstanding shares of Common Stock shall after such merger represent less than 50% of the outstanding voting shares and voting share equivalents of the merged company, or (iii) to sell or otherwise transfer all or substantially all of its assets to any person, other than Grantee or one of its Subsidiaries, then, and in each such case, the agreement governing such transaction shall make proper provision so that the Option shall, upon the consummation of any such transaction and upon the terms and conditions set forth herein, be converted into, or exchanged for, an option (the “Substitute Option”), at the election of the Holder, of either (x) the Acquiring Corporation (as hereinafter defined) or (y) any person that controls the Acquiring Corporation.

(b) The following terms have the meanings indicated:

(A) “Acquiring Corporation” shall mean (i) the continuing or surviving person of a consolidation or merger with Issuer (if other than Issuer), (ii) Issuer in a merger in which Issuer is the continuing or surviving person, and (iii) the transferee of all or substantially all of Issuer’s assets.

(B) “Substitute Common Stock” shall mean the common stock issued by the issuer of the Substitute Option upon exercise of the Substitute Option.

(D) “Average Price” shall mean the average closing price of a share of the Substitute Common Stock for the one year immediately preceding the consolidation, merger or sale in question, but in no event higher than the closing price of the shares of Substitute Common Stock on the day preceding such consolidation, merger or sale; provided that if Issuer is the issuer of the Substitute Option, the Average Price shall be computed with respect to a share of common stock issued by the person merging into Issuer or by any company which controls or is controlled by such person, as the Holder may elect.

(c) The Substitute Option shall have the same terms as the Option, provided, that if the terms of the Substitute Option cannot, for legal reasons, be the same as the Option, such terms shall be as similar as possible and in no event less advantageous to the Holder. The issuer of the Substitute Option shall also enter into an agreement with the then Holder or Holders of the Substitute Option in substantially the same form as this Agreement, which shall be applicable to the Substitute Option.

(d) The Substitute Option shall be exercisable for such number of shares of Substitute Common Stock as is equal to the Assigned Value multiplied by the number of shares of Common Stock for which the Option is then exercisable, divided by the Average Price. The exercise price of the Substitute Option per share of Substitute Common Stock shall then be equal to the Option Price multiplied by a fraction, the numerator of which shall be the number of shares of Common Stock for which the Option is then exercisable and the denominator of which shall be the number of shares of Substitute Common Stock for which the Substitute Option is exercisable.

(e) In no event, pursuant to any of the foregoing paragraphs, shall the Substitute Option be exercisable for more than 19.9% of the shares of Substitute Common Stock outstanding prior to exercise of the Substitute Option. In the event that the Substitute Option would be exercisable for more than 19.9% of the shares of Substitute Common Stock outstanding prior to exercise but for this clause (e), the issuer of the Substitute Option (the “Substitute Option Issuer”) shall make a cash payment to Holder equal to the excess of (i) the value of the Substitute Option without giving effect to the limitation in this clause (e) over (ii) the value of the Substitute Option after giving effect to the limitation in this clause (e). This difference in value shall be determined by a nationally recognized investment banking firm selected by the Holder or the Owner, as the case may be, and reasonably acceptable to the Acquiring Corporation.

(f) Issuer shall not enter into any transaction described in subsection (a) of this Section 8 unless the Acquiring Corporation and any person that controls the Acquiring Corporation assume in writing all the obligations of Issuer hereunder.

9. (a) At the request of the holder of the Substitute Option (the “Substitute Option Holder”), the Substitute Option Issuer shall repurchase the Substitute Option from the Substitute Option Holder at a price (the “Substitute Option Repurchase Price”) equal to the amount by which (i) the Highest Closing Price (as hereinafter defined) exceeds (ii) the exercise price of the Substitute Option, multiplied by the number of shares of Substitute Common Stock for which the Substitute Option may then be exercised, and at the request of the owner (the “Substitute Share Owner”) of shares of Substitute Common Stock (the “Substitute Shares”), the Substitute Option Issuer shall repurchase the Substitute Shares at a price (the “Substitute Share Repurchase Price”) equal to the Highest Closing Price multiplied by the number of Substitute Shares so designated. The term “Highest Closing Price” shall mean the highest closing price for shares of Substitute Common Stock within the six-month period immediately preceding the date the Substitute Option Holder gives notice of the required repurchase of the Substitute Option or the Substitute Share Owner gives notice of the required repurchase of the Substitute Shares, as applicable.

(b) The Substitute Option Holder and the Substitute Share Owner, as the case may be, may exercise its respective right to require the Substitute Option Issuer to repurchase the Substitute Option and the Substitute Shares pursuant to this Section 9 by surrendering for such purpose to the Substitute Option Issuer, at its principal office, the agreement for such Substitute Option (or, in the absence of such an agreement, a copy of this Agreement) and certificates for Substitute Shares accompanied by a written notice or notices stating that the Substitute Option Holder or the Substitute Share Owner, as the case may be, elects to require the Substitute Option Issuer to repurchase the Substitute Option and/or the Substitute Shares in accordance with the provisions of this Section 9. As promptly as practicable, and in any event within five business days after the surrender of the Substitute Option and/or certificates representing Substitute Shares and the receipt of such notice or notices relating thereto, the Substitute Option Issuer shall deliver or cause to be delivered to the Substitute Option Holder the Substitute Option Repurchase Price and/or to the Substitute Share Owner the Substitute Share Repurchase Price therefor or, in either case, the portion thereof which the Substitute Option Issuer is not then prohibited under applicable law and regulation from so delivering.

(c) To the extent that the Substitute Option Issuer is prohibited under applicable law or regulation from repurchasing the Substitute Option and/or the Substitute Shares in part or in full, the Substitute Option Issuer following a request for repurchase pursuant to this Section 9 shall immediately so notify the Substitute Option Holder and/or the Substitute Share Owner and thereafter deliver or cause to be delivered, from time to time, to the Substitute Option Holder and/or the Substitute Share Owner, as appropriate, the portion of the Substitute Share Repurchase Price, respectively, which it is no longer prohibited from delivering, within five business days after the date on which the Substitute Option Issuer is no longer so prohibited; provided, however, that if the Substitute Option Issuer is at any time after delivery of a notice of repurchase pursuant to subsection (b) of this Section 9 prohibited under applicable law or regulation from delivering to the Substitute Option Holder and/or the Substitute Share Owner, as appropriate, the Substitute Option Repurchase Price and the Substitute Share Repurchase Price, respectively, in full (and the Substitute Option Issuer shall use its reasonable best efforts to obtain all required regulatory and legal approvals, in each case as promptly as practicable, in order to accomplish such repurchase), the Substitute Option Holder or Substitute Share Owner may revoke its notice of repurchase of the Substitute Option or the Substitute Shares either in whole or to the extent of the prohibition, whereupon, in the latter case, the Substitute Option Issuer shall promptly (i) deliver to the Substitute Option Holder or Substitute Share Owner, as appropriate, that portion of the Substitute Option Repurchase Price or the Substitute Share Repurchase Price that the Substitute Option Issuer is not prohibited from delivering; and (ii) deliver, as appropriate, either (A) to the Substitute Option Holder, a new Substitute Option evidencing the right of the Substitute Option Holder to purchase that number of shares of the Substitute Common Stock obtained by multiplying the number of shares of the Substitute Common Stock for which the surrendered Substitute Option was exercisable at the time of delivery of the notice of repurchase by a fraction, the numerator of which is the Substitute Option Repurchase Price less the portion thereof theretofore delivered to the Substitute Option

Holder and the denominator of which is the Substitute Option Repurchase Price, or (B) to the Substitute Share Owner, a certificate for the Substitute Common Stock it is then so prohibited from repurchasing.

10. The 90-day or 180-day periods for exercise of certain rights under Sections 2, 6, 7 and 13 shall be extended: (i) to the extent necessary to obtain all regulatory approvals for the exercise of such rights and for the expiration of all statutory waiting periods; (ii) to the extent necessary to avoid liability under Section 16(b) of the 1934 Act by reason of such exercise; and (3) when there exists an Order that prohibits or delays exercise of such right.

11. Issuer hereby represents and warrants to Grantee as follows:

(a) Issuer has full corporate power and authority to execute and deliver this Agreement and to consummate the transactions contemplated hereby. The execution and delivery of this Agreement and the consummation of the transactions contemplated hereby have been duly and validly authorized by the Board of Directors of Issuer and no other corporate proceedings on the part of Issuer are necessary to authorize this Agreement or to consummate the transactions so contemplated. This Agreement has been duly and validly executed and delivered by Issuer.

(b) Issuer has taken all necessary corporate action to authorize and reserve and to permit it to issue, and at all times from the date hereof through the termination of this Agreement in accordance with its terms will have reserved for issuance upon the exercise of the Option, that number of shares of Common Stock equal to the maximum number of shares of Common Stock at any time and from time to time issuable hereunder, and all such shares, upon issuance pursuant hereto, will be duly authorized, validly issued, fully paid, nonassessable, and will be delivered free and clear of all claims, liens, encumbrance and security interests and not subject to any preemptive rights.

(c) The Board of Directors of Issuer has unanimously approved this Agreement and the transactions contemplated hereby (including by reserving shares for issuance of shares of Common Stock on exercise of the Option) and taken any other action as required to render inapplicable to such agreement and transactions Section 203 of the Delaware General Corporation Law and, to the knowledge of Issuer, any similar Takeover Statutes.

12. Grantee hereby represents and warrants to Issuer that:

(a) Grantee has all requisite corporate power and authority to enter into this Agreement and, subject to any approvals or consents referred to herein, to consummate the transactions contemplated hereby. The execution and delivery of this Agreement and the consummation of the transactions contemplated hereby have been duly authorized by all necessary corporate action on the part of Grantee. This Agreement has been duly executed and delivered by Grantee.

(b) The Option is not being, and any shares of Common Stock or other securities acquired by Grantee upon exercise of the Option will not be, acquired with a view to the public distribution thereof and will not be transferred or otherwise disposed of except in a transaction registered or exempt from registration under the 1933 Act.

13. Neither of the parties hereto may assign any of its rights or obligations under this Agreement or the Option created hereunder to any other person, without the express written consent of the other party, except that in the event a Subsequent Triggering Event shall have occurred prior to an Exercise Termination Event, Grantee, subject to the express provisions hereof, may assign in whole or in part its rights and obligations hereunder within 180 days following such Subsequent Triggering Event; provided, however, that until the date 15 days following the date on which the Federal Reserve Board approves an application by Grantee or its transferee under the BHCA to acquire the shares of Common Stock subject to the Option, Grantee may not assign its rights under the Option except in (i) a widely dispersed public distribution, (ii) a private placement in which no one party acquires the right to purchase in excess of 2% of the voting shares of Issuer, (iii) an assignment to a single party (e.g., a broker or investment banker) for the purpose of conducting a widely dispersed public distribution on Grantee’s behalf, or (iv) any other manner approved by the Federal Reserve Board.

14. Each of Grantee and Issuer will use its reasonable best efforts to make all filings with, and to obtain consents of, all third parties and governmental authorities necessary to the consummation of the transactions contemplated by this Agreement, including without limitation making application to list the shares of Common Stock issuable hereunder on the New York Stock Exchange upon official notice of issuance and applying to the Federal Reserve Board under the BHCA for approval to acquire the shares issuable hereunder, but Grantee shall not be obligated to apply to state banking authorities for approval to acquire the shares of Common Stock issuable hereunder until such time, if ever, as it deems appropriate to do so.

15. (a) Grantee may, at any time during which Issuer would be required to repurchase the Option or any Option Shares pursuant to Section 7 upon proper request or notice, surrender the Option (together with any Option Shares issued to and then owned by Grantee) to Issuer in exchange for a cash fee equal to the Surrender Price (as defined below); provided, however, that Grantee may not exercise its rights pursuant to this Section 15 if Issuer has repurchased the Option (or any portion thereof) or any Option Shares pursuant to Section 7. The “Surrender Price” shall be equal to (i) $343,962,190, plus (ii) if applicable, the aggregate purchase price previously paid pursuant hereto by Grantee with respect to any Option Shares, minus (iii) if applicable, the sum of (A) the excess of (1) the net cash amounts, if any, received by Grantee pursuant to the arms’ length sale of Option Shares (or any other securities into which such Option Shares were converted or exchanged) to any party not affiliated with Grantee, over (2) the aggregate purchase price previously paid pursuant hereto by Grantee with respect to such Option Shares and (B) the net cash amounts, if any, received by Grantee pursuant to an arms’ length sale of a portion of the Option to any party not affiliated with Grantee.

(b) Grantee may exercise its right to surrender the Option and any Option Shares pursuant to this Section 15 by surrendering to Issuer, at its principal office, this

Agreement together with certificates for Option Shares, if any, accompanied by a written notice stating (i) that Grantee elects to surrender the Option and Option Shares, if any, in accordance with the provisions of this Section 15 and (ii) the Surrender Price. The Surrender Price shall be payable in immediately available funds on or before the second business day following receipt of such notice by Issuer.

(c) To the extent that Issuer is prohibited under applicable law or regulation from paying the Surrender Price to Grantee in full, Issuer shall immediately so notify Grantee and thereafter deliver or cause to be delivered, from time to time, to Grantee, the portion of the Surrender Price that Issuer is no longer prohibited from paying, within five business days after the date on which Issuer is no longer so prohibited, provided, however, that if Issuer at any time after delivery of a notice of surrender pursuant to paragraph (b) of this Section 15 is prohibited under applicable law or regulation from paying to Grantee the Surrender Price in full (i) Issuer shall (A) use its reasonable best efforts to obtain all required regulatory and legal approvals and to file any required notices as promptly as practicable in order to make such payments, (B) within five days of the submission or receipt of any documents relating to any such regulatory and legal approvals, provide Grantee with copies of the same, and (C) keep Grantee advised of both the status of any such request for regulatory and legal approvals, as well as any discussions with any relevant regulatory or other third party reasonably related to the same and (ii) Grantee may revoke such notice of surrender by delivery of a notice of revocation to Issuer and, upon delivery of such notice of revocation, the Exercise Termination Date shall be extended to a date six months from the date on which the Exercise Termination Date would have occurred if not for the provisions of this Section 15(c) (during which period Grantee may exercise any of its rights hereunder, including any and all rights pursuant to this Section 15).

(d) Grantee shall have rights substantially identical to those set forth in paragraphs (a), (b) and (c) of this Section 15 with respect to the Substitute Option and the Substitute Option Issuer during any period in which the Substitute Option Issuer would be required to repurchase the Substitute Option pursuant to Section 9.

16. (a) Notwithstanding any other provision of this Agreement, in no event shall the Grantee’s Total Profit (as hereinafter defined) exceed $393,099,645 and, if it otherwise would exceed such amount, the Grantee, at its sole election, shall either (i) reduce the number of shares of Common Stock subject to this Option, (ii) deliver to Issuer for cancellation Option Shares previously purchased by Grantee, (iii) pay cash to Issuer, or (iv) any combination thereof, so that Grantee’s actually realized Total Profit shall not exceed $393,099,645 after taking into account the foregoing actions.

(b) Notwithstanding any other provision of this Agreement, this Option may not be exercised for a number of shares as would, as of the date of exercise, result in a Notional Total Profit (as defined below) of more than $393,099,645; provided that nothing in this sentence shall restrict any exercise of the Option permitted hereby on any date subsequent to such initial date of exercise.

(c) As used herein, the term “Total Profit” shall mean the aggregate amount (before taxes) of the following: (i) the amount received by Grantee pursuant to Issuer’s repurchase of the Option (or any portion thereof) pursuant to Section 7, (ii) (x) the amount received by Grantee pursuant to Issuer’s repurchase of Option Shares pursuant to Section 7, less (y) the Grantee’s purchase price for such Option Shares, (iii) (x) the net cash amounts received by Grantee pursuant to the sale of Option Shares (or any other securities into which such Option Shares are converted or exchanged) to any unaffiliated party, less (y) the Grantee’s purchase price of such Option Shares, (iv) any amounts received by Grantee on the transfer of the Option (or any portion thereof) to any unaffiliated party, and (v) any amount equivalent to the foregoing with respect to the Substitute Option.

(d) As used herein, the term “Notional Total Profit” with respect to any number of shares as to which Grantee may propose to exercise this Option shall be the Total Profit determined as of the date of such proposed exercise assuming that this Option were exercised on such date for such number of shares and assuming that such shares, together with all other Option Shares held by Grantee and its affiliates as of such date, were sold for cash at the closing market price for the Common Stock as of the close of business on the preceding trading day (less customary brokerage commissions).

17. The parties hereto acknowledge that damages would be an inadequate remedy for a breach of this Agreement by either party hereto and that the obligations of the parties hereto shall be enforceable by either party hereto through injunctive or other equitable relief.

18. If any term, provision, covenant or restriction contained in this Agreement is held by a court or a federal or state regulatory agency of competent jurisdiction to be invalid, void or unenforceable, the remainder of the terms, provisions and covenants and restrictions contained in this Agreement shall remain in full force and effect, and shall in no way be affected, impaired or invalidated. If for any reason such court or regulatory agency determines that the Holder is not permitted to acquire, or Issuer is not permitted to repurchase pursuant to Section 7, the full number of shares of Common Stock provided in Section 1(a) hereof (as adjusted pursuant to Section 1(b) or 5 hereof), it is the express intention of Issuer to allow the Holder to acquire or to require Issuer to repurchase such lesser number of shares as may be permissible, without any amendment or modification hereof.

19. All notices, requests, claims, demands and other communications hereunder shall be deemed to have been duly given when delivered in person, by cable, telegram, telecopy or telex, or by registered or certified mail (postage prepaid, return receipt requested) at the respective addresses of the parties set forth in the Merger Agreement.

20. This Agreement shall be governed by and construed in accordance with the laws of the State of New York, without regard to any applicable conflicts of law principles (except to the extent that mandatory provisions of federal or state law apply).

21. This Agreement may be executed in two counterparts, each of which shall be deemed to be an original, but all of which shall constitute one and the same agreement.

22. Except as otherwise expressly provided herein, each of the parties hereto shall bear and pay all costs and expenses incurred by it or on its behalf in connection with the transactions contemplated hereunder, including fees and expenses of its own financial consultants, investment bankers, accountants and counsel.

23. Except as otherwise expressly provided herein or in the Merger Agreement, this Agreement contains the entire agreement between the parties with respect to the transactions contemplated hereunder and supersedes all prior arrangements or understandings with respect thereof, written or oral. The terms and conditions of this Agreement shall inure to the benefit of and be binding upon the parties hereto and their respective successors and permitted assigns. Nothing in this Agreement, expressed or implied, is intended to confer upon any party, other than the parties hereto, and their respective successors and permitted assigns, any rights, remedies, obligations or liabilities under or by reason of this Agreement, except as expressly provided herein.

24. Capitalized terms used in this Agreement and not defined herein shall have the meanings assigned thereto in the Merger Agreement.

IN WITNESS WHEREOF, each of the parties has caused this Agreement to be executed on its behalf by its officers thereunto duly authorized, all as of the date first above written.


REGIONS FINANCIAL CORPORATION
(Issuer)

By:		/s/ Xxxxxxx X. Xxxxx
Name:		Xxxxxxx X. Xxxxx
Title:		Chairman, President and Chief Executive Officer

AMSOUTH BANCORPORATION
(Grantee)

By:		/s/ X. Xxxx Xxxxxx
Name:		X. Xxxx Xxxxxx
Title:		Chairman, President and Chief Executive Officer

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THE TRANSFER OF THIS AGREEMENT IS SUBJECT TO CERTAIN PROVISIONS CONTAINED HEREIN AND TO RESALE RESTRICTIONS UNDER THE SECURITIES ACT OF 1933, AS AMENDED

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