Edo Castle is a flatland castle that was built in 1457 by Ōta Dōkan in Edo, Toshima District, Musashi Province. In modern times it is part of the Tokyo Imperial Palace in Chiyoda, Tokyo, and is therefore also known as Chiyoda Castle.
Tokugawa Ieyasu established the Tokugawa shogunate there, and it was the residence of the shōgun and the headquarters of the military government during the Edo period (1603–1867) in Japanese history. After the resignation of the shōgun and the Meiji Restoration, it became the Tokyo Imperial Palace. Some moats, walls and ramparts of the castle survive to this day. However, the grounds were more extensive during the Edo period, with Tokyo Station and the Marunouchi section of the city lying within the outermost moat. It also encompassed Kitanomaru Park, the Nippon Budokan Hall and other current landmarks of the surrounding area.
The warrior Edo Shigetsugu built his residence in what is now the Honmaru and Ninomaru part of Edo Castle, around the end of the Heian or beginning of the Kamakura period. The Edo clan left in the 15th century as a result of uprisings in the Kantō region, and Ōta Dōkan, a retainer of the Ogigayatsu Uesugi family, built Edo Castle in 1457.
The castle later came under the control of the Later Hōjō clan in 1524 after the Siege of Edo. The castle was vacated in 1590 due to the Siege of Odawara. Tokugawa Ieyasu made Edo Castle his base after he was offered eight eastern provinces by Toyotomi Hideyoshi. He later defeated Toyotomi Hideyori, son of Hideyoshi, at the Siege of Osaka in 1615, and emerged as the political leader of Japan. Tokugawa Ieyasu received the title of Sei-i Taishōgun in 1603, and Edo became the center of Tokugawa's administration.
Initially, parts of the area were lying under water. The sea reached the present Nishinomaru area of Edo Castle, and Hibiya was a beach. The landscape was changed for the construction of the castle. Most construction started in 1593 and was completed in 1636 under Ieyasu's grandson, Tokugawa Iemitsu.