The Parliament of the United Kingdom of Great Britain and Northern Ireland is the supreme legislative body of the United Kingdom, and may also legislate for the Crown Dependencies and the British Overseas Territories. It meets at the Palace of Westminster in London. Parliament possesses legislative supremacy and thereby holds ultimate power over all other political bodies in the United Kingdom and the Overseas Territories. While Parliament is bicameral, it has three parts: the sovereign, the House of Lords, and the House of Commons. The three parts acting together to legislate may be described as the King-in-Parliament. The Crown normally acts on the advice of the prime minister, and the powers of the House of Lords are limited to only delaying legislation; thus power is de facto vested in the House of Commons.

The monarchy of the United Kingdom, commonly referred to as the British monarchy, is the form of government used by the United Kingdom by which a hereditary monarch reigns as the head of state, with their powers regulated by the British Constitution. The term may also refer to the role of the royal family within the UK's broader political structure. The current monarch is King Charles III, who ascended the throne on 8 September 2022, upon the death of his mother, Queen Elizabeth II.