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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 10-K

OR

Commission File Number 1-3610

ALCOA INC.

(Exact name of registrant as specified in its charter)

Registrant’s telephone numbers:

Investor Relations (212) 836-2674

Office of the Secretary (412) 553-4707

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act: None

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months, and (2) has been subject to such filing requirements for the past 90 days. Yes  þ  No  ¨.

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K. ¨

Indicate by check mark whether the registrant is an accelerated filer (as defined in Rule 12b-2 of the Act). Yes  þ  No ¨.

The aggregate market value of the outstanding common stock, other than shares held by persons who may be deemed affiliates of the registrant, as of the last business day of the registrant’s most recently completed second fiscal quarter was approximately $28 billion. As of January 13, 2003, there were 844,925,354 shares of common stock, par value $1.00 per share, of the registrant outstanding.

Documents incorporated by reference.

Parts I, II and IV of this Form 10-K incorporate by reference certain information from the registrant’s 2002 Annual Report to Shareholders (Annual Report). Part III of this Form 10-K incorporates by reference certain information from the registrant’s definitive Proxy Statement dated February 20, 2003 (Proxy Statement).

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Note on Incorporation by Reference

In this Form 10-K, selected items of information and data are incorporated by reference to portions of the Annual Report. Any reference in this report to disclosures in the Annual Report shall constitute incorporation by reference of that specific disclosure into this Form 10-K.

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ALCOA INC.

Formed in 1888 under the laws of the Commonwealth of Pennsylvania, Alcoa Inc. has its registered office in Pittsburgh, Pennsylvania. In this report, unless the context otherwise requires, Alcoa or the “company” means Alcoa Inc. and all subsidiaries consolidated for the purposes of its financial statements.

The company’s Internet address is http://www.alcoa.com. Alcoa makes available free of charge on or through its website its annual report on Form 10-K, quarterly reports on Form 10-Q, current reports on Form 8-K, and amendments to those reports filed or furnished pursuant to Section 13(a) or 15(d) of the Securities Exchange Act of 1934 as soon as reasonably practicable after the company electronically files such material with, or furnishes it to, the Securities and Exchange Commission.

PART I

Item 1. Business.

Description of the Business

Information describing Alcoa’s businesses can be found in the Annual Report at the indicated pages:

Item

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Structure of Certain Operations

The company’s Alumina and Chemicals segment primarily consists of a series of affiliated operating entities referred to as Alcoa World Alumina and Chemicals (AWAC). Generally, Alcoa owns 60% and Alumina Limited (formerly WMC Limited) owns 40% of these entities. In December 2002, WMC Limited (WMC), an Australian mining and minerals processing company, demerged into two separate listed companies, Alumina Limited and WMC Resources Ltd. Alumina Limited is the successor to WMC for holding WMC’s interest in AWAC. For more information on AWAC, see Exhibit Nos. 10(a) through 10(e) to this report.

Alcoa owns 59.1% of Alcoa Aluminio S.A. (Aluminio), an integrated aluminum producer in Brazil. Aluminio operates mining, refining, smelting and fabricated products facilities at various locations in Brazil. The remaining 40.9% of Aluminio is principally held through direct and indirect ownership by companies controlled by the Camargo Correa Group, a leading contractor and industrial conglomerate in Brazil.

Bauxite Interests

Aluminum is one of the most plentiful metals in the earth’s crust. Aluminum is produced primarily from bauxite, an ore containing aluminum in the form of aluminum oxide, commonly referred to as alumina. Aluminum is made by extracting alumina from bauxite and then removing oxygen from the alumina. Alcoa processes most of the bauxite that it mines into alumina. The company obtains bauxite from reserves held by AWAC, from the company’s interests in Brazil, and under both long-term and short-term contracts and mining leases. In 2002, Alcoa consumed 30.3 million metric tons (mt) of bauxite from its own reserves, 5.7 million mt from related third parties and 1.5 million mt from unrelated third parties. Alcoa’s present sources of bauxite are sufficient to meet the forecasted requirements of its alumina refining operations for the foreseeable future. The following table provides information regarding the company’s bauxite interests:

Alcoa Active¹ Bauxite Interests

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Alumina Refining Facilities and Capacity

Alcoa is the world’s leading producer of alumina. Alcoa’s alumina refining facilities and its worldwide alumina capacity are shown in the following table:

Alumina Refining Capacity

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In October 2002, Alcoa and BHP Billiton signed a non-binding letter of intent (LOI) formalizing cooperation on various mining and refining opportunities in Suriname. The LOI covers the continuation of mining and refining of bauxite in eastern Suriname beyond the existing term of the joint venture agreement (2006). The LOI also contemplates a 250,000 mtpy expansion to be commenced in 2003 at the existing 1.95 million mtpy refinery, and exploration over the next two years of bauxite mining and refining opportunities in western Suriname. Alcoa and BHP Billiton plan to own 55% and 45%, respectively, of all bauxite and alumina joint venture interests in Suriname, which is the current arrangement at the existing refinery.

In January 2003, Alcoa and BHP Billiton also signed a Memorandum of Understanding (MOU) with the government of Suriname providing for various exploration and other activities over the next two years relating to the feasibility of bauxite and alumina investment in western Suriname. Under the MOU, Alcoa and BHP Billiton have exclusive rights in western Suriname and have committed to spend up to $8.5 million over the next 21-25 months to investigate this opportunity, shared 55% (Alcoa) and 45% (BHP Billiton). The MOU provides that Alcoa and BHP Billiton will negotiate an investment agreement with the government within 18 months.

Primary Aluminum Facilities and Capacity

The company’s primary aluminum smelters and their respective capacities are shown in the following table:

Alcoa Worldwide Smelting Capacity

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