Tokyo, (東京 Tōkyō, English: /, Japanese: [toːkʲoː] (listen)) officially Tokyo Metropolis (東京都 Tōkyō-to), is one of the 47 prefectures of Japan. It has served as the Japanese capital since 1869. As of 2018 , the Greater Tokyo Area ranked as the most populous metropolitan area in the world. The urban area houses the seat of the Emperor of Japan, of the Japanese government and of the National Diet. Tokyo forms part of the Kantō region on the southeastern side of Japan's main island, Honshu, and includes the Izu Islands and Ogasawara Islands. Tokyo was formerly named Edo when Shōgun Tokugawa Ieyasu made the city his headquarters in 1603. It became the capital after Emperor Meiji moved his seat to the city from Kyoto in 1868; at that time Edo was renamed Tokyo. The Tokyo Metropolis formed in 1943 from the merger of the former Tokyo Prefecture (東京府 Tōkyō-fu) and the city of Tokyo (東京市 Tōkyō-shi). Tokyo is often referred to as a city but is officially known and governed as a "metropolitan prefecture", which differs from and combines elements of a city and a prefecture, a characteristic unique to Tokyo.
The 23 Special Wards of Tokyo were formerly Tokyo City. On July 1, 1943, it merged with Tokyo Prefecture and became Tokyo Metropolis with an additional 26 municipalities in the western part of the prefecture, and the Izu islands and Ogasawara islands south of Tokyo. As of October 1, 2015, the population of Tokyo is estimated to be over 13.4 million, or about 11% of Japan's total population. The latest estimate in 2019 shows the growing population of Tokyo with 13.9 million people, with the special wards 9.6 million, the Tama area 4.2 million, and the Islands 25,147. The prefecture is part of the world's most populous metropolitan area called the Greater Tokyo Area with over 40 million people and the world's largest urban agglomeration economy. As of 2011 , Tokyo hosted 51 of the Fortune Global 500 companies, the highest number of any city in the world at that time. Tokyo ranked third (twice) in the International Financial Centres Development Index. The city is home to various television networks such as Fuji TV, Tokyo MX, TV Tokyo, TV Asahi, Nippon Television, NHK and the Tokyo Broadcasting System.
Tokyo ranks first in the Global Economic Power Index and third in the Global Cities Index. The GaWC's 2018 inventory classified Tokyo as an alpha+ world city  – and as of 2014 TripAdvisor's World City Survey ranked Tokyo first in its "Best overall experience" category (the city also ranked first in the following categories: "helpfulness of locals", "nightlife", "shopping", "local public transportation" and "cleanliness of streets"). As of 2018 Tokyo ranked as the 2nd-most expensive city for expatriates, according to the Mercer consulting firm. and also the world's 11th-most expensive city according to the Economist Intelligence Unit's cost-of-living survey. In 2015, Tokyo was named the Most Liveable City in the world by the magazine Monocle. The Michelin Guide has awarded Tokyo by far the most Michelin stars of any city in the world. Tokyo was ranked first out of all sixty cities in the 2017 Safe Cities Index. It was also ranked the first in the 2019 safe cities index. The QS Best Student Cities ranked Tokyo as the 3rd-best city in the world to be a university student in 2016 and 2nd in 2018. Tokyo hosted the 1964 Summer Olympics, the 1979 G-7 summit, the 1986 G-7 summit, and the 1993 G-7 summit, and will host the 2019 Rugby World Cup, the 2020 Summer Olympics and the 2020 Summer Paralympics.
Tokyo was originally known as Edo (江戸), which means "estuary". Its name was changed to Tokyo (東京 Tōkyō, 東 tō "east", and 京 kyō "capital") when it became the imperial capital with the arrival of Emperor Meiji in 1868, in line with the East Asian tradition of including the word capital (京) in the name of the capital city (like Kyoto (京都), Beijing (北京) and Nanjing (南京)). During the early Meiji period, the city was also called "Tōkei", an alternative pronunciation for the same characters representing "Tokyo", making it a kanji homograph. Some surviving official English documents use the spelling "Tokei"; however, this pronunciation is now obsolete.