The Parliament Act 1911 is an act of the Parliament of the United Kingdom. It is constitutionally important and partly governs the relationship between the House of Commons and the House of Lords, the two Houses of Parliament. The Parliament Act 1949 provides that the Parliament Act 1911 and the Parliament Act 1949 are to be construed together "as one" in their effects and that the two acts may be cited together as the Parliament Acts 1911 and 1949.

An Act of Parliament in the United Kingdom is primary legislation passed by the UK Parliament in Westminster, London.