During the subsequent Edo period, Edo grew into one of the largest cities in the world with a population topping one million by the 18th century.
When he became shōgun in 1603, Edo became the center of his ruling. In 1590, Tokugawa Ieyasu moved from Mikawa Province (his lifelong base) to the Kantō region. Edo was first fortified by the Edo clan, in the late twelfth century. Tokyo was originally a small fishing village called Edo, in what was formerly part of the old Musashi Province. Some surviving official English documents use the spelling "Tokei" however, this pronunciation is now obsolete. During the early Meiji period, the city was sometimes called "Tōkei", an alternative pronunciation for the same characters representing "Tokyo", making it a kanji homograph. During the Meiji Restoration in 1868, the name of the city was changed to Tokyo ( 東京, from 東 tō "east", and 京 kyō "capital"), when it became the new imperial capital, in line with the East Asian tradition of including the word capital ( 京) in the name of the capital city (for example, Kyoto ( 京都), Keijō ( 京城), Beijing ( 北京), Nanjing ( 南京), and Xijing ( 西京)). The name, which can be translated as " estuary", is a reference to the original settlement's location at the meeting of the Sumida River and Tokyo Bay. Tokyo was originally known as Edo ( 江戸), a kanji compound of 江 ( e, "cove, inlet") and 戸 ( to, "entrance, gate, door"). Notable districts of Tokyo include Chiyoda (the site of the Imperial Palace), Shinjuku (the city's administrative center), and Shibuya (a commercial, cultural and business hub). Shinjuku Station is also the world's busiest train station.
Tokyo Station is the central hub for Japan's Shinkansen bullet train system, and the city is served by an extensive network of rail and subways. Tokyo is an international center of research and development and is represented by several major universities, notably the University of Tokyo. The city has hosted multiple international events, including the 1964 Summer Olympics and Paralympics, the postponed 2020 Summer Olympics and Paralympics and three G7 Summits (1979, 1986, and 1993). The Tokyo Metro Ginza Line is the oldest underground metro line in East Asia (1927). Tokyo has the world's tallest tower, Tokyo Skytree, and the world's largest underground floodwater diversion facility, MAOUDC.
In 2020, it ranked fourth on the Global Financial Centres Index, behind New York City, London, and Shanghai. In 2019, it hosted 36 of the Fortune Global 500 companies. Part of an industrial region that includes the cities of Yokohama, Kawasaki, and Chiba, Tokyo is Japan's leading center of business and finance. Tokyo is the largest urban economy in the world by gross domestic product, and is categorized as an Alpha+ city by the Globalization and World Cities Research Network. Since 1943, the Tokyo Metropolitan Government has administered the prefecture's 23 special wards (formerly Tokyo City), various bed towns and suburbs in the western area, and two outlying island chains. Beginning in the 1950s, the city underwent rapid reconstruction and expansion, going on to lead Japan's post-war economic recovery. Tokyo was devastated by the 1923 Great Kantō earthquake, and again by Allied bombing raids during World War II. Following the end of the shogunate in 1868, the imperial capital in Kyoto was moved to the city, which was renamed Tokyo (literally "eastern capital"). By the mid-18th century, Edo was one of the most populous cities in the world at over one million. Originally a fishing village, named Edo, the city became a prominent political center in 1603, when it became the seat of the Tokugawa shogunate. The Greater Tokyo Area is the most populous metropolitan area in the world, with an estimated 37.468 million residents in 2018. As of 2021, the prefecture has an estimated population of 14.04 million. Tokyo is the political and economic center of the country, as well as the seat of the Emperor of Japan and the national government. Located at the head of Tokyo Bay, the prefecture forms part of the Kantō region on the central Pacific coast of Japan's main island of Honshu. Tokyo ( / ˈ t oʊ k i oʊ/, Japanese: 東京, Tōkyō ( listen)), historically known in the West as Tokio and officially the Tokyo Metropolis ( 東京都, Tōkyō-to), is the capital, the largest city, and the most populous metropolitan area in the Greater Tokyo Area, the Kantō region, and Japan, as well as the most populous metropolitan area in the world and most populous prefecture of Japan.