A civil union is a legally recognized relationship between members of a same-sex couple, with rights similar to those of a marriage relationship.
As of the knowledge cutoff in 2023, the state of Missouri does not recognize civil unions. Missouri law defines marriage as a union between two persons, regardless of their sex, following the U.S. Supreme Court's decision in Obergefell v. Hodges (2015), which legalized same-sex marriage nationwide. This landmark ruling effectively provided same-sex couples with the same legal rights and responsibilities as those afforded to opposite-sex couples in marriage, rendering the need for a separate civil union status largely moot. Therefore, same-sex couples in Missouri can enter into a marriage rather than a civil union, and they are entitled to all the legal benefits and protections that marriage provides.