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 Rhode Island, which is not a community property state but rather an equitable distribution state, marital property is not automatically considered to be owned jointly by both spouses. Instead, marital property is distributed equitably, though not necessarily equally, in the event of a divorce. A marital property partition agreement, also known as a postnuptial agreement in Rhode Island, is a legal document that allows married spouses to designate certain marital assets as the separate property of one spouse. This agreement must be in writing and typically requires full disclosure of assets and voluntary consent by both parties. It is enforceable if it is fair and reasonable at the time of execution and remains fair and reasonable at the time of divorce. If spouses cannot agree on the division of property, a Rhode Island court can partition the property in a divorce proceeding, taking into account factors such as the length of the marriage, the conduct of the parties during the marriage, and each spouse's contribution to the acquisition, preservation, or appreciation in value of their respective estates.