Underwriting Agreement

Exhibit 1.1

Spansion Inc.

42,200,000 Shares ^a/

Class A Common Stock

($0.001 par value)

Underwriting Agreement

New York, New York

December 15, 2005

Citigroup Global Markets Inc.

Credit Suisse First Boston LLC

As Representatives of the several Underwriters,

388 Greenwich Street

New York, New York 10013

Ladies and Gentlemen:

Spansion Inc., a corporation incorporated under the laws of Delaware (the “ Company ”), proposes to sell to the several underwriters named in Schedule I hereto (the “ Underwriters ”), for whom you (the “ Representatives ”) are acting as representatives, 42,200,000 shares of Class A Common Stock, par value $0.001 per share (“ Common Stock ”) of the Company (said shares to be issued and sold by the Company being hereinafter called (the “ Underwritten Securities ”). The Company also proposes to grant to the Underwriters an option to purchase up to 5,064,000 additional shares of Common Stock to cover over-allotments (the “ Option Securities ”; the Option Securities, together with the Underwritten Securities, being hereinafter called the “ Securities ”). To the extent there are no additional Underwriters listed on Schedule I other than you, the term Representatives as used herein shall mean you, as Underwriters, and the terms Representatives and Underwriters shall mean either the singular or plural as the context requires. Certain terms used herein are defined in Section 17 hereof.

1. Representations and Warranties. The Company represents and warrants to, and agrees with, each Underwriter as set forth below in this Section 1.

(a) The Company has prepared and filed with the Commission a registration statement (file number 333-124041) on Form S-1, including a related preliminary prospectus, for registration under the Act of the offering and sale of the Securities. Such Registration Statement, including any amendments thereto filed prior to the Execution Time, has become effective. The Company may have filed one or more amendments thereto, including a related preliminary prospectus, each of which has previously been furnished to you. The Company will file with the Commission a final prospectus in accordance with Rule 424(b). As filed, such final prospectus shall contain all information required by the Act and the rules thereunder and, except to the extent the Representatives shall agree in writing to a modification, shall be in all material respects in the form furnished to you prior to the Execution Time or, to the extent not completed at the Execution Time, shall contain only such specific additional information and other changes (beyond that contained in the latest Preliminary Prospectus) as the Company has advised you, prior to the Execution Time, will be included or made therein.

(b) On the Effective Date, the Registration Statement did, and when the Prospectus is first filed (if required) in accordance with Rule 424(b) and on the Closing Date (as defined herein) and on any date on which Option Securities are purchased, if such date is not the Closing Date (a “ settlement date ”), the Prospectus (and any supplements thereto) will, comply in all material respects with the applicable requirements of the Act and the rules thereunder; on the Effective Date and at the Execution Time, the Registration Statement did not contain any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary in order to make the statements therein not misleading; and on the date of any filing pursuant to Rule 424(b) and on the Closing Date and any settlement date, the Prospectus (together with any supplement thereto) will not include any untrue statement of a material fact or omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading; provided , however , that the Company makes no representations or warranties as to the information contained in or omitted from the Registration Statement, or the Prospectus (or any supplement thereto) in reliance upon and in conformity with information furnished in writing to the Company by or on behalf of any Underwriter through the Representatives specifically for inclusion in the Registration Statement or the Prospectus (or any supplement thereto), it being understood and agreed that the only such information furnished by any Underwriter consists of the information described as such in Section 8 hereof.

(c) (i) The Disclosure Package and the price to the public, the number of Underwritten Securities, the number of Option Securities and the underwriting discount disclosed on the cover page of the Prospectus, when taken together as a whole, and (ii) each electronic roadshow when taken together with the Disclosure Package, and the price to the public, the number of Underwritten Securities, the

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number of Option Securities and the underwriting discount disclosed on the cover page of the Prospectus, do not contain any untrue statement of a material fact or omit to state any material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading. The preceding sentence does not apply to statements in or omissions from the Disclosure Package based upon and in conformity with written information furnished to the Company by any Underwriter through the Representatives specifically for use therein, it being understood and agreed that the only such information furnished by or on behalf of any Underwriter consists of the information described as such in Section 8 hereof.

(d) (i) At the time of filing the Registration Statement and (ii) as of the Execution Time (with such date being used as the determination date for purposes of this clause (ii)), the Company was not and is not an Ineligible Issuer (as defined in Rule 405), without taking account of any determination by the Commission pursuant to Rule 405 that it is not necessary that the Company be considered an Ineligible Issuer.

(e) Each Issuer Free Writing Prospectus does not include any information that conflicts with the information contained in the Registration Statement, including any document incorporated by reference therein that has not been superseded or modified. The foregoing sentence does not apply to statements in or omissions from the Disclosure Package based upon and in conformity with written information furnished to the Company by any Underwriter through the Representatives specifically for use therein, it being understood and agreed that the only such information furnished by any Underwriter consists of the information described as such in Section 8 hereof.

(f) Each of the Company and its subsidiaries has been duly incorporated or organized, as the case may be, and is validly existing, in good standing under the laws of the jurisdiction in which it is organized with full power (corporate or otherwise), and authority to own or lease, as the case may be, and to operate its properties and conduct its business as described in the Preliminary Prospectus and the Prospectus, and is duly qualified to do business as a foreign corporation and is in good standing under the laws of each jurisdiction which requires such qualification except where the failure to be so qualified or in good standing would not reasonably be expected, individually or in the aggregate, to have a material adverse effect on the condition (financial or otherwise), prospects, earnings, businesses or properties of the Company and its subsidiaries taken as a whole, whether or not arising from transactions in the ordinary course of business (a “ Material Adverse Effect ”).

(g) The Company’s authorized equity capitalization will be as set forth in the Disclosure Package and the Prospectus; the capital stock of the Company conforms in all material respects to the description thereof contained therein; the outstanding shares of Common Stock have been duly and validly authorized and issued and fully paid and nonassessable; the Securities have been duly and validly

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authorized, and, when issued and delivered to and paid for by the Underwriters pursuant to this Agreement, will be fully paid and nonassessable; the certificates for the Securities will be in valid and sufficient form; the holders of outstanding shares of capital stock of the Company are not entitled to preemptive or other rights to subscribe for the Securities; and, except as set forth in the Disclosure Package and the Prospectus, no options, warrants or other rights to purchase, agreements or other obligations to issue, or rights to convert any obligations into or exchange any securities for, shares of capital stock of or ownership interests in the Company are outstanding.

(h) All the outstanding shares of capital stock of each subsidiary have been duly and validly authorized and issued and are fully paid and nonassessable, and, except as otherwise set forth in the Disclosure Package and the Prospectus, all outstanding shares of capital stock of the subsidiaries are owned by the Company either directly or through wholly owned subsidiaries free and clear of any perfected security interest or any other security interests, claims, liens or encumbrances, except for shares of any direct or indirect subsidiary of the Company held by directors or nominees pursuant to the requirements of the law of the jurisdiction of incorporation of such subsidiary and which in the aggregate represent less than one percent of the outstanding capital stock of such subsidiary.

(i) There is no franchise, contract or other document of a character required to be described in the Registration Statement or Prospectus, or to be filed as an exhibit thereto, which is not described or filed as required (the Disclosure Package contained in all material respects the same descriptions of the foregoing matters contained in the Prospectus); and the statements in the Preliminary Prospectus and the Prospectus under the headings “Certain U.S. Federal Tax Considerations for Non-U.S. Holders” and “Description of Capital Stock”, insofar as such statements summarize legal matters, agreements, documents or proceedings discussed therein, are accurate and fair summaries of such legal matters, agreements, documents or proceedings.

(j) The Company is not and, after giving effect to the offering and sale of the Securities and the application of the proceeds thereof as described in the Prospectus, will not be an “investment company” as defined in the Investment Company Act of 1940, as amended.

(k) No consent, approval, authorization, filing with or order of any court or governmental agency or body is required in connection with the transactions contemplated herein and such as may be required under the blue sky laws of any jurisdiction in connection with the issuance and sale of the Securities to the Underwriters in the manner contemplated herein and in the Prospectus.

(l) Neither the issuance and sale of the Securities nor the consummation of any other of the transactions herein contemplated nor the fulfillment of the terms hereof will conflict with, result in a breach or violation of, or imposition of any lien, charge or encumbrance upon any property or assets of

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the Company or any of its subsidiaries, as the case may be, pursuant to, (i) the charter or by-laws of the Company or any of its subsidiaries, as the case may be, (ii) the terms of any indenture, contract, lease, mortgage, deed of trust, note agreement, loan agreement or other agreement, obligation, condition, covenant or instrument to which the Company or any of its subsidiaries is a party or bound or to which its or their property is subject, or (iii) any statute, law, rule, regulation, judgment, order or decree applicable to the Company or any of its subsidiaries of any court, regulatory body, administrative agency, governmental body, arbitrator or other authority having jurisdiction over the Company or any of its subsidiaries or any of its or their properties which violation would, in the cases of clauses (ii) and (iii) of this Section (1)(l), have a Material Adverse Effect or a material adverse effect on the transaction contemplated hereby.

(m) No holders of securities of the Company have rights to the registration of such securities under the Registration Statement.

(n) The consolidated historical financial statements and schedules of the Company and its consolidated subsidiaries included in the Preliminary Prospectus, the Prospectus and the Registration Statement present fairly in all material respects the financial condition, results of operations and cash flows of the Company and its consolidated subsidiaries as of the dates and for the periods indicated, comply as to form in all material respects with the applicable accounting requirements of the Act and have been prepared in conformity with generally accepted accounting principles in the United States applied on a consistent basis throughout the periods involved (except as otherwise noted therein). The selected financial data set forth under the caption “Selected Historical Consolidated Financial Data” in the Preliminary Prospectus, the Prospectus and Registration Statement fairly present in all material respects, on the basis stated in the Preliminary Prospectus, the Prospectus and the Registration Statement, the information included therein. The pro forma financial statements included in the Preliminary Prospectus, the Prospectus and the Registration Statement include assumptions that provide a reasonable basis for presenting the significant effects directly attributable to the transactions and events described therein, the related pro forma adjustments give appropriate effect to those assumptions, and reflect the proper application of those adjustments to the historical financial statement amounts in the pro forma financial statements included in the Preliminary Prospectus, the Prospectus and the Registration Statement. The pro forma financial statements included in the Preliminary Prospectus, the Prospectus and the Registration Statement comply as to form in all material respects with the applicable accounting requirements of Regulation S-X under the Act.

(o) No action, suit or proceeding by or before any court or governmental agency, authority or body or any arbitrator involving the Company or any of its subsidiaries or its or their property is pending or, to the best knowledge of the Company, threatened that (i) could reasonably be expected to have a Material Adverse Effect on the performance of this Agreement or the

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consummation of any of the transactions contemplated hereby or (ii) could reasonably be expected to have a Material Adverse Effect, except as set forth in or contemplated in the Disclosure Package and the Prospectus (exclusive of any supplement thereto).

(p) Each of the Company and each of its subsidiaries owns or leases all such properties as are necessary to the conduct of its operations as presently conducted.

(q) Neither the Company nor any subsidiary is in violation or default of (i) any provision of its operating agreement, charter or bylaws, as the case may be, (ii) the terms of any indenture, contract, lease, mortgage, deed of trust, note agreement, loan agreement or other agreement, obligation, condition, covenant or instrument to which it is a party or bound or to which its property is subject, or (iii) any statute, law, rule, regulation, judgment, order or decree of any court, regulatory body, administrative agency, governmental body, arbitrator or other authority having jurisdiction over the Company or such subsidiary or any of its properties, as applicable which violation or default would, in the case of clauses (ii) or (iii), have a Material Adverse Effect.

(r) Ernst & Young LLP which have certified certain financial statements of the Company and its consolidated subsidiaries and delivered their report with respect to the audited consolidated financial statements and schedules included in the Prospectus, are independent public accountants with respect to the Company within the meaning of the Act and the applicable published rules and regulations thereunder.

(s) There are no transfer taxes or other similar fees or charges under Federal law or the laws of any state, or any political subdivision thereof, required to be paid in connection with the execution and delivery of this Agreement or the issuance by the Company or sale by the Company of the Securities.

(t) The Company has filed all non-U.S., U.S. federal, state and local tax returns that are required to be filed or has requested extensions thereof (except in any case in which the failure so to file would not have a Material Adverse Effect, except as set forth in or contemplated in the Disclosure Package and the Prospectus (exclusive of any supplement thereto)) and has paid all taxes required to be paid by it and any other assessment, fine or penalty levied against it, to the extent that any of the foregoing is due and payable, except for any such assessment, fine or penalty that is currently being contested in good faith or as would not have a Material Adverse Effect, except as set forth in or contemplated in the Disclosure Package and Prospectus (exclusive of any supplement thereto).

(u) No labor problem or dispute with the employees of the Company or any of its subsidiaries exists or is threatened or, to the knowledge of the Company, imminent, except as would not have a Material Adverse Effect.

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(v) The Company and each of its subsidiaries are insured by insurers of recognized financial responsibility against such losses and risks and in such amounts as are prudent and customary in the businesses in which they are engaged; all policies of insurance and fidelity or surety bonds insuring the Company or any of its subsidiaries or their respective businesses, assets, employees, officers and directors are in full force and effect; the Company and its subsidiaries are in compliance with the terms of such policies and instruments in all material respects; and there are no claims by the Company or any of its subsidiaries under any such policy or instrument as to which any insurance company is denying liability or defending under a reservation of rights clause; neither the Company nor any such subsidiary has been refused any insurance coverage sought or applied for; and neither the Company nor any such subsidiary has any reason to believe that it will not be able to renew its existing insurance coverage as and when such coverage expires or to obtain similar coverage from similar insurers as may be necessary to continue its business at a cost that would not have a Material Adverse Effect, except as set forth in or contemplated in the Disclosure Package and the Prospectus (exclusive of any supplement thereto).

(w) No subsidiary of the Company is currently prohibited, directly or indirectly, from paying any dividends to the Company, from making any other distribution on such subsidiary’s capital stock, from repaying to the Company any loans or advances to such subsidiary from the Company or from transferring any of such subsidiary’s property or assets to the Company or any other subsidiary of the Company, except as described in or contemplated by the Disclosure Package and the Prospectus (exclusive of any supplement thereto).

(x) The Company and its subsidiaries possess all licenses, certificates, permits and other authorizations issued by the appropriate federal, state or foreign regulatory authorities necessary to conduct their respective businesses, and neither the Company nor any such subsidiary has received any notice of proceedings relating to the revocation or modification of any such certificate, authorization or permit which, absence, singly or in the aggregate, if the subject of an unfavorable decision, ruling or finding, would have a Material Adverse Effect, except as set forth in or contemplated in the Disclosure Package and the Prospectus (exclusive of any supplement thereto).

(y) The Company and each of its subsidiaries maintain a system of internal accounting controls sufficient to provide reasonable assurance that (i) transactions are executed in accordance with management’s general or specific authorizations; (ii) transactions are recorded as necessary to permit preparation of financial statements in conformity with generally accepted accounting principles and to maintain asset accountability; (iii) access to assets is permitted only in accordance with management’s general or specific authorization; and (iv) the recorded accountability for assets is compared with the existing assets at reasonable intervals and appropriate action is taken with respect to any differences.

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(z) The Company has not taken, directly or indirectly, any action designed to or that would constitute or that might reasonably be expected to cause or result in, under the Exchange Act or otherwise, stabilization or manipulation of the price of any security of the Company to facilitate the sale or resale of the Securities.

(aa) The Company and its subsidiaries are (i) in compliance with any and all applicable non-U.S., U.S. federal, state and local laws and regulations relating to the protection of human health and safety, the environment or hazardous or toxic substances or wastes, pollutants or contaminants (“ Environmental Laws ”), (ii) have received and are in compliance with all permits, licenses or other approvals required of them under applicable Environmental Laws to conduct their respective businesses and (iii) have not received notice of any actual or potential liability under any environmental law, except where such non-compliance with Environmental Laws, failure to receive required permits, licenses or other approvals, or liability would not, individually or in the aggregate, have a Material Adverse Effect, except as set forth in or contemplated in the Disclosure Package and the Prospectus (exclusive of any supplement thereto). Except as set forth in the Disclosure Package and the Prospectus, neither the Company nor any of the subsidiaries has been named as a “potentially responsible party” under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, as amended.

(bb) In the ordinary course of its business, the Company periodically reviews the effect of Environmental Laws on the business, operations and properties of the Company and its subsidiaries, in the course of which it identifies and evaluates associated costs and liabilities (including, without limitation, any capital or operating expenditures required for clean-up, closure of properties or compliance with Environmental Laws, or any permit, license or approval, any related constraints on operating activities and any potential liabilities to third parties). On the basis of such review, the Company has reasonably concluded that such associated costs and liabilities would not, singly or in the aggregate, have a Material Adverse Effect, except as set forth in or contemplated in the Disclosure Package and the Prospectus (exclusive of any supplement thereto).

(cc) Except as set forth in the Disclosure Package and the Prospectus, neither the Company nor any of its subsidiaries has violated the Employee Retirement Income Security Act of 1974, as amended, and the regulation and published interpretations thereunder, or similar non-U.S. laws, except for violations which, singly, or in the aggregate, would not have a Material Adverse Effect. Neither the Company or any entity which is under common control with Company (as determined under Section 414 of the Code sponsors or has sponsored a plan subject to Title IV of ERISA.

(dd) There is and has been no failure on the part of the Company and any of the Company’s directors or officers, in their capacities as such, to comply with any provision of the Sarbanes Oxley Act of 2002 and the rules and

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regulations promulgated in connection therewith that are in effect as of the date hereof (the “ Sarbanes Oxley Act ”), including Section 402 related to loans and Sections 302 and 906 related to certifications.

(ee) Neither the Company nor any of its subsidiaries nor, to the knowledge of the Company, any director, officer, agent, employee or Affiliate of the Company or any of its subsidiaries is aware of or has taken any action, directly or indirectly, that would result in a material violation by such Persons of the FCPA, including, without limitation, making use of the mails or any means or instrumentality of interstate commerce corruptly in furtherance of an offer, payment, promise to pay or authorization of the payment of any money, or other property, gift, promise to give, or authorization of the giving of anything of value to any “foreign official” (as such term is defined in the FCPA) or any foreign political party or official thereof or any candidate for foreign political office, in contravention of the FCPA and the Company, its subsidiaries and, to the knowledge of the Company, its Affiliates have conducted their businesses in compliance with the FCPA and have instituted and maintain policies and procedures designed to ensure, and which are reasonably expected to continue to ensure, continued compliance therewith.

“FCPA” means Foreign Corrupt Practices Act of 1977, as amended, and the rules and regulations thereunder.

(ff) The operations of the Company and its subsidiaries are and have been conducted at all times in compliance with applicable financial recordkeeping and reporting requirements of the Currency and Foreign Transactions Reporting Act of 1970, as amended, the money laundering statutes of all jurisdictions, the rules and regulations thereunder and any related or similar rules, regulations or guidelines, issued, administered or enforced by any governmental agency (collectively, the “ Money Laundering Laws ”) and no action, suit or proceeding by or before any court or governmental agency, authority or body or any arbitrator involving the Company or any of its subsidiaries with respect to the Money Laundering Laws is pending or, to the best knowledge of the Company, threatened.

(gg) Neither the Company nor any of its subsidiaries nor, to the knowledge of the Company, any director, officer, agent, employee or Affiliate of the Company or any of its subsidiaries is currently subject to any U.S. sanctions administered by the Office of Foreign Assets Control of the U.S. Treasury Department (“ OFAC ”); and the Company will not directly or indirectly use the proceeds of the offering, or lend, contribute or otherwise make available such proceeds to any subsidiary, joint venture partner or other person or entity, for the purpose of financing the activities of any person currently subject to any U.S. sanctions administered by OFAC.

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(hh) The subsidiaries listed on Annex A attached hereto are the only significant subsidiaries of the Company as defined by Rule 1-02 of Regulation S-X (the “ Subsidiaries ”).

(ii) The Company and its subsidiaries own, possess, license or have other rights to use all patents, patent applications, trade and service marks, trade and service mark registrations, trade names, copyrights, licenses, inventions, trade secrets, technology, know-how and other intellectual property (collectively, the “ Intellectual Property ”) necessary for the conduct of their respective businesses as now conducted or as proposed in the Disclosure Package and the Prospectus to be conducted except where the failure to own or possess or otherwise be able to acquire such Intellectual Property would not, singly or in the aggregate, have a Material Adverse Effect. Except as set forth in the Disclosure Package and the Prospectus, (i) there is no material infringement by third parties of any such Intellectual Property; (ii) to the knowledge of the Company, there is no pending or threatened action, suit, proceeding or claim by others challenging the rights of the Company or any of its subsidiaries in or to any such Intellectual Property; (iii) to the knowledge of the Company, there is no pending or threatened action, suit, proceeding or claim by others challenging the validity or scope of any such Intellectual Property; (iv) to the knowledge of the Company, there is no pending or threatened action, suit, proceeding or claim by others that the Company infringes or otherwise violates any patent, trademark, copyright, trade secret or other proprietary rights of others; (v) to the knowledge of the Company, there is no U.S. patent or published U.S. patent application which contains claims that dominate or may dominate any Intellectual Property described in the Disclosure Package and the Prospectus as being owned by or licensed to the Company or any of its subsidiaries or that interferes with the issued or pending claims or any such Intellectual Property; and (vi) there is no prior art of which the Company is aware that may render any U.S. patent held by the Company or any of its subsidiaries invalid or any U.S. patent application held by the Company or any of its subsidiaries unpatentable which has not been disclosed to the U.S. Patent and Trademark Office, except for the foregoing items set forth in clauses (i) through (vi) of this subparagraph, which would not, individually or in the aggregate, have a Material Adverse Effect, whether or not arising from transactions in the ordinary course of business.

(jj) Except as disclosed in the Registration Statement, the Disclosure Package and the Prospectus, the Company (i) does not have any material lending or other relationship with any bank or lending Affiliate of any Underwriter and (ii) does not intend to use any of the proceeds from the sale of the Securities hereunder to repay any outstanding debt owed to