Colonial Office, a department established by the British government to administer its colonial possessions, including British North America. It established forms of government and the church, appointed governors, approved local laws and made grants for particular purposes. It managed "imperial subjects" such as commerce and shipping, which gradually came under the exclusive control of the self-governing colonies.

Between the 1660s and 1768 British colonies had been governed by a combination of the secretary of state for the southern department and the Board of Trade and Plantations, a committee within the Privy Council. In 1768 the American or Colonial Department was established, but this office was abolished in 1782 after the loss of the American colonies (see American Revolution). Jurisdiction over the remainder of British possessions was transferred to the home secretary's office until 1801, when colonial administration was moved to the secretary of state for war and the colonies.

Colonial affairs expanded and became more important, and in 1825 a permanent undersecretary was appointed to deal with the colonies. This marks the beginning of the Colonial Office, although a separate secretary of state for the colonies was not created until 1854, after the Crimean War began. Further reorganization occurred as the range of powers claimed by the colonies expanded and as relations with these colonies became diplomatic rather than administrative.

A Dominion division within the Colonial Office dealt with the self-governing colonies between 1907 and 1 July 1925, when it became a separate ministry, the Secretary of State for Dominion Affairs. In 1947 this became the Commonwealth Relations Office, which in 1966 merged with the Colonial Office. Finally, in 1968, Britain combined the responsibility for all its external relations in the single Foreign and Commonwealth Office.

See also Commonwealth.