In the U.S., the legal rights of a mistress—meaning someone in a romantic relationship with a person who is already married—are quite limited, but there are a few exceptions depending on the circumstances and the state.

- Palimony (in some cases): In a few states, if the couple lived together and there was an implied or written agreement for financial support, the mistress might be able to claim palimony—a form of financial support similar to alimony but for unmarried partners.