The is a railway line of East Japan Railway Company (JR East) in Tokyo, Japan. It is one of Tokyo's busiest and most important lines, connecting most of Tokyo's big stations and city centres, including Marunouchi, the Yūrakuchō/Ginza area, Shinagawa, Shibuya, Shinjuku, Ikebukuro and Ueno, with all but two of its 29 stations connecting to other railway or underground (subway) lines. 