This article argues for separating the institutions of marriage and parenting, conceptually and legally. Marriage is neither necessary nor adequate for fostering cooperative and stable co‐parenting. Because promoting marriage fails to protect all children, the state should develop a more suitable formal mechanism whereby co‐parents can commit to cooperate in good faith in order to best serve the interests of their children. Like civil marriage, many of the terms of these contracts are aspirational and not enforceable, though they can guide arrangements for custody and financial support. Co‐parenting agreements need not be limited to two parents, nor need they be limited to legal parents, but can include de facto parents, such as stepparents, foster parents, and other support parents. One important aim of these agreements is to recognise and support the valuable work that married or unmarried co‐parents perform, and to protect the parental rights of caregivers in different kinds of situations.