A Dominion was any of several self-governing nations of the British Empire. With the evolution of the British Empire into the Commonwealth of Nations, the dominions became independent states.
"Dominion status" was first accorded to Canada, Australia, New Zealand, Newfoundland, South Africa, and the Irish Free State at the 1926 Imperial Conference through the Balfour Declaration of 1926, recognising Great Britain and the Dominions as "autonomous within the British Empire, equal in status, in no way subordinate one to another in any aspect of their domestic or external affairs, though united by a common allegiance to the Crown and freely associated as members of the British Commonwealth of Nations". Their full legislative independence was subsequently confirmed in the 1931 Statute of Westminster. Later India, Pakistan, and Ceylon (now Sri Lanka) also became dominions, for short periods of time.
With the transition of the British Empire into the Commonwealth of Nations after World War II, it was decided that the term Commonwealth country should formally replace dominion for official Commonwealth usage. This decision was made during the 1949 Commonwealth Prime Ministers' Conference when India was intending to become a republic, so that both types of governments could become and remain full members of the Commonwealth, and this term hence refers to the autonomous dominions and republics.
After this, the term dominion without its legal dimension stayed in use for thirty more years for Commonwealth countries which had the crown as head of state, before gradually, particularly after 1953, being replaced by the term realm, as equal realms of the crown of the Commonwealth.
The term dominion means "that which is mastered or ruled". It was used by the British to describe their colonies or territorial possessions.
Use of dominion to refer to a particular territory within the British Empire dates back to the 16th century and was sometimes used to describe Wales from 1535 to around 1800: for instance, the Laws in Wales Act 1535 applies to "the Dominion, Principality and Country of Wales".