The Commonwealth secretary-general is the head of the Commonwealth Secretariat, the central body which has served the Commonwealth of Nations since its establishment in 1965, and responsible for representing the Commonwealth publicly. The Commonwealth secretary-general should not be confused with the head of the Commonwealth.

The Commonwealth Secretariat is the main intergovernmental agency and central institution of the Commonwealth of Nations. It is responsible for facilitating co-operation between members; organising meetings, including the Commonwealth Heads of Government Meetings (CHOGM); assisting and advising on policy development; and providing assistance to countries in implementing the decisions and policies of the Commonwealth.