The Palace of Westminster is the meeting place of the Parliament of the United Kingdom and is located in London, England. It is commonly called the Houses of Parliament after the House of Commons and the House of Lords, the two legislative chambers which occupy the building. The palace is the centre of political life in the United Kingdom; "Westminster" has become a metonym for the UK Parliament and the British Government, and the Westminster system of government commemorates the name of the palace. The clock bell in the Elizabeth Tower of the palace, nicknamed Big Ben, is a landmark of London and the United Kingdom in general. The Palace of Westminster has been a Grade I listed building since 1970 and part of a UNESCO World Heritage Site since 1987.

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.