A marital property partition agreement—also known as a partition and exchange agreement, a postmarital agreement, or a postnuptial agreement—is an agreement between spouses during marriage to convert marital property (also known as community property in some states) to one spouse’s separate property.

Property that is jointly owned by spouses or domestic partners (often owned as joint tenants with a right of survivorship) may also be partitioned or divided in a lawsuit or court action rather than by agreement of the spouses.

Laws regarding marital property partition agreements vary from state to state and are generally located in a state’s statutes—often in the family code or domestic relations code.

In North Dakota, marital property is not recognized as community property, as North Dakota is an 'equitable distribution' state rather than a community property state. This means that in the event of a divorce, marital property is divided equitably, but not necessarily equally, by the courts. A marital property partition agreement in North Dakota, also known as a postnuptial agreement, allows married spouses to agree on how their property should be classified (as separate or marital) and divided in the event of a divorce. Such agreements must be in writing and are subject to certain legal requirements to be enforceable, including full disclosure of assets and voluntary signing without coercion. If spouses wish to partition or divide jointly owned property without a court action, they can do so through a written agreement, but it must comply with North Dakota's contract laws and property laws. If they cannot agree, the court will decide on the division of property during divorce proceedings, taking into account factors such as the length of the marriage, the contributions of each spouse, and the economic circumstances of each party.