The Alcoa Building (also known as Regional Enterprise Tower) is a 120-meter-high skyscraper located in downtown Pittsburgh, Pennsylvania. It was completed in 1953 and has 31 floors. It is the fifteenth tallest building in the city[1] and is located next to Mellon Square. It was designed by the architectural firm Harrison & Abramovitz.[2]​ The roof contains a unique radiant heating and cooling system: since there are no pipes, radiators or air conditioning units along the exterior walls, an additional 1,400 m² of rentable space was obtained.[2]​ Additionally, the windows rotate 360 ​​degrees so that they can be washed from the inside.[3]​.

It was originally the headquarters of the Aluminum Company of America (Alcoa). The building's aluminum walls are 1/8 inch thick, giving it a lightweight and economical design.[2] It was the first skyscraper with an all-aluminum façade. Following Alcoa's relocation in 2001 to a new headquarters building on Pittsburgh's North Shore near PNC Park Stadium, the former Alcoa Building became home to government entities, regional nonprofit organizations, and small business startups, including RIDC.[4] In 2016, the top half of the building (floors 14 to 31) was converted to apartments, known as The Residences at the Historic Alcoa Building.[5]​.

• - Annex: Tallest buildings in Pittsburgh.

• - Annex: Tallest buildings in Pennsylvania.