Yes, prenups are legal, although in Australia they are called “Financial Agreements” which are made before marriage. The Family Law Act 1975 (the Act) gives couples the option to enter into a legally binding Agreement in relation to how assets are to be dealt with should the relationship break down and the marriage come to an end.
Section 90B of the Act deals with Financial Agreements made between people who are contemplating entering into a marriage.
As long as the parties to the agreement comply with Section 90G of the Act, the financial agreement will be binding on the parties.