4/C, also known as 4th & Columbia, is a proposed supertall skyscraper in Seattle, Washington, United States. If built, the 1,020-foot-tall (310 m), 91-story tower would be the tallest in Seattle, surpassing the neighboring Columbia Center, and the first supertall in the Pacific Northwest. The project has been under development by Miami-based Crescent Heights since 2015 and undergone several design changes and modifications under three architecture firms. As of 2023, 4/C is expected to have 1,090 residential units—apartments up to the 64th floor and condominiums from the 65th to 90th floor—along with several coworking and retail spaces. The latest version was designed by Skidmore, Owings & Merrill.