Жапонияның Сибу Шинжуку темір жол желісі

Railway line in Japan operated by Seibu railway

The Seibu Shinjuku Line (西武新宿線) 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. The Shinjuku Line is one of two main lines of the Seibu Railway system along with the Ikebukuro Line. The two main lines cross at Tokorozawa Station in Tokorozawa, Saitama. The line serves the western suburbs of Tokyo, connecting them to Shinjuku and other areas of downtown Tokyo.

The line is mostly double track, except for 1.1 km (1200 yards) of single track between Wakita Junction and Hon Kawagoe Station. While the section from Seibu Shinjuku to Takadanobaba is elevated, the line runs at ground level through a suburban area until Saginomiya.

Seven types of train service are operated on the line: Local, Semi Express, Express, Commuter Express, Rapid Express, Haijima Liner, and Koedo limited express, as shown below. Limited Express trains use Seibu 10000 series EMUs, and a supplementary limited express ticket is required. In addition, operation of the all seat reserved train "Haijima Liner" using the Seibu 40000 series EMU started from March of 2018. The "Haijima Liner" operates from Seibu Shinjuku to Haijima on weekends and in both directions on weekdays. There are regular through operations to the Haijima Line. There are also occasional through services to Seibukyūjō mae Station in order to bring fans to the Seibu Dome for Saitama Seibu Lions baseball games. The Seibu Shinjuku Line is one of the few major commuter rail lines in Tokyo that does not have through service to the Tokyo Metro or Toei Subway network. Through service onto the Seibu Kokubunji Line has been suspended since 19 March 2019 because of the reconstruction of Higashi Murayama Station into an elevated station.

In the 1980s, Seibu drew up a plan to build an underground line for express trains between Seibu Shinjuku and Kami Shakujii, including a new underground station between Seibu Shinjuku and the Metro Promenade. This plan was indefinitely postponed in 1995 due to costs and a decline in passenger ridership versus previous projections.

During the 1960s, Seibu unsuccessfully negotiated with the Teito Rapid Transit Authority to offer through service between the Seibu Shinjuku Line and Tozai Line. Seibu's approach was rejected in favor of through operation with the Chuo Main Line. In September 2020, Seibu Railway President Kimio Kitamura said during an interview with the Toyo Keizai that there have been many complaints from passengers heading to the city center on the Seibu Shinjuku Line and Seibu is considering various options to address this issue, such as getting through service into the Tokyo Metro Tozai Line.

Initial work has started on grade separating the line from Nogata to Iogi Stations and from Iogi to Seibu Yagisawa Stations. Proposals are being done to for grade separating the line from Tanashi to Hanakoganei Stations and from Takadanobaba to Nakai Stations.