Elizabeth II is Queen of the United Kingdom and has been since 1952.
Current reigning monarchs by length of reign . Elizabeth II is the current longest-reigning monarch , having been Queen of the United Kingdom , Canada , Australia and New Zealand since 6 February 1952 . Elizabeth II . She has seen major constitutional changes , such as devolution in the United Kingdom , Canadian patriation , and the decolonisation of Africa . This is a list of British monarchs by longevity since the Union of the Crowns of England , Scotland and Ireland in 1603 . United Kingdom . The United Kingdom is a constitutional monarchy with a parliamentary system of governance . The monarch is Queen Elizabeth II , who has reigned since 6 February 1952 .