The Nambu Line (南武線, Nanbu-sen^?) is a Japanese railway line which connects Tachikawa Station in Tachikawa, Tokyo and Kawasaki Station in Kawasaki, Kanagawa Prefecture. For most of its length, it parallels the Tama River, the natural border between Tokyo and Kanagawa prefectures. It is part of the East Japan Railway Company (JR East) network. The name refers to the southern (南, nan^?) part of the ancient province of Musashi (武蔵^?) (now Tokyo and northern Kanagawa prefectures), through which the Nambu Line runs.

Rapid service trains (two trains per hour between 10 a.m. and 4 p.m) do not stop at Shitte, Yakō, Hirama, Mukaigawara, Tsudayama, Kuji and Shukugawara. All other trains except for some seasonal services are local trains, stopping at all stations.

The "Shitte crossover" (尻手短絡線, Shitte-tanraku-sen^?) connects Shitte Station and Shin-Tsurumi Yard on the Tōkaidō Main Line (Hinkaku Line) and the Musashino Line. Freight trains operating between Tokyo Freight Terminal and northern Japan operate on both branch lines.