The firm will buy an estimated 1.2TWh/year output from developer Eolus Vind’s Øyfjellet project for 15 years.
Alcoa said the deal will cover the electricity needed by its production facility in Mosjøen, central Norway.
Construction of the Øyfjellet site is due to start this year and due to be commissioned in 2021, Eolus added.
The developer has not announced which turbines are to be used at the site.
Eolus CEO Per Witalisson said: "Øyfjellet is a great place for wind power, and we are pleased to have taken this important step towards the realisation of one of the largest wind farms in the Nordic region together with Alcoa."
Øyvind Isachsen, CEO of the Norwegian Wind Energy Association (NORWEA) added: "This is a project that underlines the love story between wind-power and the power-intensive (aluminium) industry.
"From Alcoa’s smelter, you will be able to look up onto the turbines at Øyfjellet feeding competitive renewable power into the plant."
Alcoa had also previously signed a power purchase agreement (PPA) for an unspecified capacity from developer Norsk Miljøkraft’s 281MW Nordlicht project, which is to be installed across two neighbouring mountains west of the city of Tromso in the north of Norway.