The Nambu Line is a Japanese railway line which connects Tachikawa Station in Tachikawa, Tokyo and Kawasaki Station in Kawasaki, Kanagawa. For most of its length, it parallels the Tama River, the natural border between Tokyo and Kanagawa prefectures. It lies along the Tama Hills. It is part of the East Japan Railway Company network. The line forms part of what JR East refers to as the "Tokyo Mega Loop" around Tokyo, consisting of the Keiyo Line, Musashino Line, Nambu Line, and the Yokohama Line. The name refers to the southern part of the ancient province of Musashi, through which the Nambu Line runs.

The Yokohama Line is a Japanese railway line of the East Japan Railway Company connecting Higashi-Kanagawa Station in Yokohama, Kanagawa and Hachiōji Station in Hachiōji, Tokyo. The line forms part of what JR East refers to as the "Tokyo Mega Loop" around Tokyo, consisting of the Keiyo Line, Musashino Line, Nambu Line, and Yokohama Line. The line's name comes from the section between Nagatsuta and Higashi-Kanagawa that runs through the city of Yokohama. Nicknamed the Hama-sen (浜線) by locals, the line serves commuters in the southwestern suburbs of Tokyo and northeastern suburbs of Yokohama.