The Nambu Line (南武線) is a railway line of the East Japan Railway Company (JR East). It links Tachikawa Station with Kawasaki Station, by crossing and then following the Tama River, the border between Tokyo and Kanagawa Prefectures.

Tachikawa Station is a transfer point for the (Chuo Main Line, Ome Line, Itsukaichi Line, and Tama Toshi Monorail Line). Kawasaki Station is a transfer point for the Tokaido Main Line and Keihin-Tohoku Line.

The name comes from Nan (south) and Bu (Musashi Province): the Nambu Line serves the southern part of Musashi.