The Greater Tokyo Area is a large metropolitan area in Japan consisting of most of the prefectures of Chiba, Kanagawa, Saitama, and Tokyo (at the center). In Japanese, it is referred to as various terms, including the Tokyo Area, National Capital Region, One Metropolis, Three Prefectures, and others.

It is the world's most populous metropolitan area (35,197,000 at 2005 estimate blank">United Nations World Urbanization Prospects (2005 edition) ), covering an area of approximately 13,500 km² (5,200 mi²). Japan Statistics Bureau - Keihin'yō Major Metropolitan Area It is the second largest in the world in terms of built-up or urban function landmass at 7,800 km² (3,000 mi²). (Only the urban area surrounding _New York City at 8,700 km² is larger). It has 35 cities with 200,000 people or more, 21 cities with at least 300,000 people, and 10 with over 500,000 people. It is first in the world in terms of railed transit usage, with 22 million passengers using rail as their primary means of travel daily on its 136 predominantly heavy rail lines.