Paul G. Allen (born January 21, 1953) is a co-founder of Microsoft Corporation (together with Bill Gates). He regularly appears on lists of the richest people in the world.

He is the owner of the Portland Trail Blazers, an NBA basketball team, and the Seattle Seahawks, of the National Football League. He is also one of the principal financiers behind the SETI project, having stepping in to rescue the project when NASA stopped funding it in the 1990s.

Allen runs a venture capital firm, Vulcan Ventures, and has created the Experience Music Project, a museum of music history, in Seattle, Washington.

He (through Vulcan Ventures) owns TechTV and (through Rose City Radio Corporation) some Portland radio stations. When he heard Seattle's Cinerama movie theater was about to shut down, he bought, restored, and updated it into a showplace for movies of all formats.

In December 2003 he announced that he was the sponsor behind the SpaceShipOne private rocket plane venture from Scaled Composites, as part of the X-Prize competition.

In September 2003, Allen founded the Allen Institute of Brain Science pledging $100 million in seed money to the Seattle-based organization. Its inaugural project is the Allen Brain Atlas, a map of the human brain which will be made publicly accessible.