Ascension Island is part of the British Overseas Territory of St Helena, Ascension and Tristan da Cunha under the sovereignty of the British Crown. The territory is presided over by a Governor, appointed by HM the Queen, who is resident on St Helena. The Governor is represented on Ascension by the Administrator. A revised Constitution entered into force in September 2009. An elected Island Council advises the Governor on laws, policies and the government's annual budget.

Ascension, like the United Kingdom's other Overseas Territories and the Crown Territories, is not part of the United Kingdom. It has its own Constitution (shared with St Helena and Tristan da Cunha), is internally self-governing, makes its own laws and as a separate fiscal jurisdiction, has tax raising powers through the Governor. The United Kingdom is responsible for defence, international relations and internal security.