The Parliament Acts are two Acts of Parliament of the United Kingdom, passed in 1911 and 1949, that form part of the Constitution of the United Kingdom.

The first Parliament Act, the Parliament Act 1911 (1 & 2 Geo. 5. c. 13), asserted the supremacy of the House of Commons by limiting the legislation-blocking powers of the House of Lords (the suspensory veto). Provided the provisions of the Act are met, legislation can be passed without the approval of the House of Lords. Additionally, the 1911 Act amended the Septennial Act to reduce the maximum permitted time between general elections from seven years to five years. The first Parliament Act was amended by the second Parliament Act, the Parliament Act 1949 (12, 13 & 14 Geo. 6. c. 103), which further limited the power of the Lords by reducing the time that they could delay bills, from two years to one. (SN/PC/675) (last updated 10 September 2004, in PDF format, 24 pages)

The Parliament Acts have been used to pass legislation against the wishes of the House of Lords on only seven occasions since 1911, including the passing of the Parliament Act 1949. Some constitutional lawyers had questioned the validity of the 1949 Act; these doubts were settled in 2005 when members of the Countryside Alliance unsuccessfully challenged the validity of the Hunting Act 2004, which had been passed under the auspices of the Act. In October 2005, the House of Lords dismissed the Alliance's appeal against this decision, with an unusually large panel of nine Law Lords holding that the 1949 Act was a valid Act of Parliament.