A prenuptial agreement, sometimes referred to as an antenuptial agreement, but commonly abbreviated to prenup, is a contract entered into by two people prior to marriage or civil union. The content of a prenuptial agreement can vary widely, but commonly includes provisions for the division of property should the couple divorce and any rights to spousal support during or after the dissolution of marriage.

Prenuptial agreements were made legal in Australia after the Family Law Act was altered in December 2000.

There are two types of prenups: marriage contract for people who are married or about to be married, and cohabitation agreements for unmarried couples.