The Shōnan–Shinjuku Line is a passenger railway service in Japan which commenced in December 2001. The line has no dedicated track as services run through shared sections along the Ryōmō Line, Takasaki Line, Utsunomiya Line, Yamanote freight line, Yokosuka Line, and Tōkaidō Main Line. It is treated as a distinct service at stations and on railway maps.

The Ryōmō Line is a Japanese railway line connecting Oyama in Tochigi Prefecture with Maebashi in Gunma Prefecture. 84.4 km (52.4 mi) long, the line is owned and operated by the East Japan Railway Company. The name refers to the fact that Gunma and Tochigi prefectures were once part of an ancient province called Keno (毛野), which was later split into Kōzuke (Gunma) and Shimotsuke (Tochigi). This line connects both halves of the old province.