The Keiō Line is a 37.9-kilometer (23.5 mi) railway line in western Tokyo, Japan, owned by the private railway operator Keiō Corporation. It connects Shinjuku, Tokyo, with the suburban city of Hachiōji. The Keiō Line is part of a network with interchanges and through running to other lines of Keiō Corporation: the Keiō New Line, Keiō Sagamihara Line, the Keiō Keibajō Line, the Keiō Dōbutsuen Line, the Keiō Takao Line, and the 1,067 mm gauge Keiō Inokashira Line.

Keio Corporation is a private railway operator in Tokyo, Japan, and the central firm of the Keio Group that is involved in transport, retail, real estate and other industries.