Seibu Railway Company, Ltd. is a conglomerate based in Tokorozawa, Saitama, Japan, with principal business areas in railways, tourism, and real estate. Seibu Railway's operations are concentrated in northwest Tokyo and Saitama Prefecture; the name "Seibu" is an abbreviation of "west Musashi", referring to the historic name for this area. It and its holding company hold shares of numerous bus, hotel and tourism operations nationwide.

The Seibu Shinjuku Line is a Japanese railway line owned by the private railway operator Seibu Railway, connecting Seibu Shinjuku Station in Shinjuku, Tokyo with Hon-Kawagoe Station in Kawagoe, Saitama.