In the Commonwealth of Nations, a high commissioner is the senior diplomat, generally ranking as an ambassador, in charge of the diplomatic mission of one Commonwealth government to another. Instead of an embassy, the diplomatic mission is generally called a high commission.

The Commonwealth of Nations, often simply referred to as the Commonwealth, is an international association of 56 member states, the vast majority of which are former territories of the British Empire from which it developed. They are connected through their use of the English language and historical-cultural ties. The chief institutions of the organisation are the Commonwealth Secretariat, which focuses on intergovernmental aspects, and the Commonwealth Foundation, which focuses on non-governmental relations among member states. Numerous organisations are associated with and operate within the Commonwealth.