Tokyo, officially Tokyo Metropolis is one of the 47 prefectures of Japan. Tokyo is the capital of Japan, the center of the Greater Tokyo Area, and the most populous metropolitan area in the world. It is the seat of the Japanese government and the Imperial Palace, and the home of the Japanese Imperial Family. Tokyo is in the Kanto region on the south eastern side of the main island Honshu and includes the Izu Islands and Ogasawara Islands. Tokyo Metropolis was formed in 1943 from the merger of the former Tokyo Prefecture and the city of Tokyo.
Tokyo is often referred to and thought of as a city, but is officially known and governed as a "metropolitan prefecture", which differs from and combines elements of both a city and a prefecture; a characteristic unique to Tokyo. The Tokyo metropolitan government administers the 23 Special Wards of Tokyo (each governed as an individual city), which cover the area that was formerly the City of Tokyo before it merged and became the subsequent metropolitan prefecture in 1943. The metropolitan government also administers 39 municipalities in the western part of the prefecture and the two outlying island chains. The population of the special wards is over 9 million people, with the total population of the prefecture exceeding 13 million. The prefecture is part of the world's most populous metropolitan area with upwards of 35 million people and the world's largest urban agglomeration economy. The city hosts 51 of the Fortune Global 500 companies, the highest number of any city.
The city is considered an alpha+ world city, listed by the GaWC's 2008 inventory and ranked fourth among global cities by A.T. Kearney's 2012 Global Cities Index. In 2013, Tokyo was named the third most expensive city for expatriates, according to the Mercer consulting firm, and the world's most expensive city, according to the Economist Intelligence Unit's cost-of-living survey. In 2009 Tokyo was named the third Most Liveable City and the World's Most Livable Megalopolis by the magazine Monocle