1000 Second Avenue, Office skyscraper in Downtown Seattle, United States

1000 Second Avenue is a 493 ft (150 m) skyscraper completed in 1987 with 43 floors, the 23rd tallest building in Seattle as of 2021. Its northwest edge forms a curved corner, and plazas are arranged in receding stacked terraces facing south. It was designed by NBBJ principal Donald Winkelmann.

Construction of this office tower began in 1984, marking a new phase of business development in downtown Seattle. The project followed fire prevention studies conducted on the previous structure at the site.

The tower's names came from its tenants: it opened as Seattle Trust Tower, became Key Tower in 1987 when Key Bank bought Seattle Trust, and reverted to its address after Key Bank left in 1991. Its largest current tenant is U.S. Immigration and Customs Enforcement.

The tower occupies the block of Second Avenue between Madison and Spring streets, with its curved northwest edge facing the avenue. The main entrance is on Second Avenue, and the receding terraced plazas step down toward the south side of the site. Visitors arriving on foot reach it from the downtown core along Second Avenue.

Since 2012, the exterior of this tower has served as a venue for annual rappelling events that support Washington Special Olympics. This unusual connection makes the building more than just an office space.