A prenuptial agreement or antenuptial agreement, commonly abbreviated to prenup or prenupt, 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 marriagee

There are two types of prenuptial agreements: marriage contract for people who are married or about to be married, and cohabitation agreement for unmarried couples. A variation for people who are already married is a postnuptial agreement.

Laws around the world vary in their recognition of such agreements.

Historically, judges in the United States frowned upon prenuptial agreements as corrupting what marriage was supposed to stand for, and often they would not recognize them. Nowadays they are recognized, although they may not always be enforced. It is common to have legal advice to the effect that both parties should have lawyers present during the signing, for a judge to ensure that neither party has been coerced into the agreement.

Prenuptial agreements are, at best, a partial solution to obviating some of the risks of marital property disputes in times of divorce. They are not the final word.