The Greater Tokyo Area in Japan is the most populous metropolitan area in the world. Tokyo is one of Japan's 47 prefectures and capital city. Tokyo is also the seat of the emperor of Japan and the Japanese government. Tokyo includes the Izu Islands and Ogasawara Islands in the Kanto region on the southeastern side of the main island Honshu. Since 1603, when Shogun Tokugawa Ieyasu made the Edo (Tokyo has formerly known as Edo) city his headquarters, Tokyo has been the de facto seat of government. Tokyo officially became the capital when, in 1868, Emperor Meiji moved his seat from the old capital of Kyoto. After this change in capitals, Edo was renamed Tokyo. After the merger of the former Tokyo Prefecture and the city of Tokyo, Tokyo metropolis was formed in 1943. The city of Tokyo hosts 51 Fortune Global 500 companies. This number is the highest of any city in the world. Various television networks such as Fuji TV, Tokyo MX, TV Tokyo, TV Asahi, Nippon Television, NHK and the Tokyo Broadcasting System were also hosted by Tokyo city. Tokyo is placed third in the International Financial Centres Development Index.

Tokyo is known and governed as a “metropolitan prefecture” but often referred to as a city. Tokyo being called a metropolitan prefecture combines elements of a city and a prefecture which is a unique characteristic of Tokyo. There are 23 special wards of Tokyo which are governed as an individual city. These wards cover the area which was the city of Tokyo before the merger. The Tokyo government also have 39 municipalities and two outlying island chains under its governance. The population fo Tokyo exceeds over 13 million with over 9 million people in the special wards. This population makes Tokyo the world's largest urban agglomeration economy.

The official intercensal estimate showed 13.506 million people in Tokyo as of October 2012. Out of these 13.506 million, 9.214 million people live within Tokyo's 23 wards. Because workers and students from adjacent areas commute to Tokyo, the population swell by over 2.5 million during the daytime. The effect of people commuting was more pronounced in the three central wards of Chiyoda, Chuo, and Minato. The population of these areas was 326,000 at night in comparison of 2.4 million during the day according to the 2005 National Census. According to the 2012 census, there were 161,169 Chinese nationals, 99,880 South Koreans and 27,929 Philippines nationals were registered with Tokyo government among 364,653 foreign nationals. The population of Tokyo is estimated to be 13.491 million as of October 2015.