The Marriage Amendment (Definition and Religious Freedoms) Act 2017 is an Act of the Parliament of Australia, which legalises same-sex marriage in Australia by amending the Marriage Act 1961 to allow marriage between two persons of marriageable age, regardless of their gender. Introduced as a private member's bill by Western Australian Senator Dean Smith of the Liberal Party following the Australian Marriage Law Postal Survey, the bill passed the Parliament on 7 December 2017. It received royal assent on the following day and came into effect on 9 December 2017.