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.

The East Japan Railway Company is a major passenger railway company in Japan, the largest of the seven Japan Railways Group companies. The company name is officially abbreviated as JR-EAST or JR East in English, and as JR Higashi-Nihon in Japanese. The company's headquarters are in Yoyogi, Shibuya, Tokyo, next to Shinjuku Station. It is listed in the Tokyo Stock Exchange, is a constituent of the TOPIX Large70 index, and is one of three Japan Railways Group constituents of the Nikkei 225 index, the others being JR Central and JR West.