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 my knowledge cutoff date in 2023, Oklahoma does not recognize civil unions. The state only recognizes marriage, which is defined as a legal union between one man and one woman. This definition was solidified by a constitutional amendment in 2004 when Oklahoma voters approved a ban on same-sex marriage and civil unions. However, the U.S. Supreme Court ruling in Obergefell v. Hodges in 2015 legalized same-sex marriage nationwide, effectively overriding state bans. As a result, same-sex couples in Oklahoma can marry and have the same legal rights as opposite-sex couples, but there is no separate legal status for civil unions in the state.