The Chūō-Sōbu Line is a railway line that runs through Tokyo and Chiba Prefecture, Japan. Part of the East Japan Railway Company network, the line operates on separate tracks along the right-of-way of the Chūō Main Line and Sōbu Main Line, providing service between Mitaka Station in the cities of Mitaka and Musashino and Chiba Station in Chiba.

The East Japan Railway Company is a major passenger railway company in Japan, the largest of the seven Japan Railways Group companies. The company name is officially abbreviated as JR-EAST or JR East in English, and as JR Higashi-Nihon in Japanese. The company's headquarters are in Yoyogi, Shibuya, Tokyo, next to Shinjuku Station. It is listed in the Tokyo Stock Exchange, is a constituent of the TOPIX Large70 index, and is one of three Japan Railways Group constituents of the Nikkei 225 index, the others being JR Central and JR West.