The current Imperial Palace stands on the site of Edo Castle, which was built in 1457 by Ota Dokan on the site of an earlier structure, captured in 1590 by Tokugawa Ieyasu, and rebuilt in the early 16th century to become the most magnificent castle in the country (see Castles).

The massive six-storey donjon was destroyed and other parts of the castle were badly damaged in the Great Meireki Fire (Meireki no Taika) of 1657, one of the worst disasters in Japanese history which destroyed about 75 per cent of the city and took the lives of between 100,000 and 200,000 people. The donjon was never rebuilt, but the shogun’s palace and other parts of the castle were reconstructed, and served as the residence of the Tokugawa down to 1868.

With the restoration of Imperial authority and the transfer of the seat of government from Kyoto to Edo (now renamed as Tokyo or ‘Eastern Capital’) in 1868, the old Tokugawa palace became the imperial residence, and in the following year both the palace and the surrounding castle buildings acquired the name Kou-jo (Imperial Castle). Just four years later in 1873 the whole complex was seriously damaged by fire, forcing the emperor to relocate temporarily to the Akasaka Palace, where he remained until 1889. Construction of a new palace began in 1884, and this was completed in time for the promulgation of the Meiji Constitution of 1889. From 1889 until 1948 the imperial palace and castle grounds were known as Kyu-jo (Palace Castle).

Some 27 imperial palace buildings were destroyed by incendiary bombs on 25-26 May 1945 during the last B-29 air raid on Tokyo. The office of the Imperial Household Agency, a modern three-storey building constructed in 1935, was then used as temporary accommodation for the imperial court until 1968, when a new ferro-concrete palace was built amidst the surviving moats, walls and ramparts of Edo Castle to a modern design with minimal Japanese architectural detail. Since 1948 the imperial palace has been known as Kokyo (Imperial Palace).