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