One of the six constituent companies of JR, Japan's national railway network. "JR East," as it's sometimes called, is listed in the Guinness Book of World Records as the world's largest passenger railway company: it has 80,000 employees and runs 1,700 stations, 13,000 trains, and 7,500 kilometers of track. On an average day, its network is used by 16 million passengers: in FY 2003, the company reported ticket revenues of nearly ¥1.8 trillion (US$16.5 billion).

In addition to managing a sprawling commuter network in and around Tokyo, JR East also runs intercity services throughout the northern panhandle of Honshu Island, going as far west as Nagano and Kofu before giving up authority to the Central Japan Railway. The Shinkansen services that run north of Tokyo Station are also administered by the East Japan Railway.

The lines in their jurisdiction are (deep breath now...):