The Marriage Act 1961 (Cth) is an Act of the Parliament of Australia which regulates marriage in Australia. Since its passage in 1961, it has been amended on numerous occasions and applies uniformly throughout Australia (including its external territories); and any law made by a state or territory inconsistent with the Act is invalid. The Act was made pursuant to power granted to the federal parliament under s.51(xxi) of the Australian Constitution. Although the federal parliament was given the power to pass laws about marriage at federation in 1901, it did not use this power until the adoption of the Act, while before 1961, each Australian state and territory had its own marriage laws.