|Area||2,187 km² (45)|
Prior to 1943, Tokyo was the name of both one of the 47 prefectures of Japan, Tokyo-fu, and the populous city of Tokyo in the eastern half of the prefecture. In 1943 the city and prefecture were merged into a unique prefectural level government entity, known as Tōkyō-to 東京都 or "Tokyo Metropolis". This administrative region includes the twenty-three "special wards" of the former city, many suburban cities in the western half of the prefecture, and two chains of islands extending south into the Pacific Ocean. About 12 million people, 10 percent of Japan's population, live within Tōkyō-to's prefectural boundaries.
About 35 million people live in the Greater Tokyo Area which encompasses Tōkyō-to and surrounding prefectures, making it the world's most populous metropolitan area. Because of its huge population and wealth, many world records are or were held here, including the most expensive real estate ever ($1.5 million/sq meter in 1990), the most expensive city for over a decade running, the most passengers served by its train system, and has the largest GDP of any metropolitan area in the world.
Tokyo is considered one of the world's major global cities and a megacity. The word "Tokyo" may refer to Tōkyō-to as a whole, or only to the main urban mass under its jurisdiction (thus excluding west Tama and Izu / Ogasawara Islands), or even the whole of Greater Tokyo Area, depending on context. This article refers to Tōkyō-to unless otherwise stated.