Same-sex marriage is legal in the U.S. state of California. The state first issued marriage licenses to same-sex couples June 16, 2008 as a result of the Supreme Court of California finding in In re Marriage Cases that barring same-sex couples from marriage violated the state's Constitution. The issuance of such licenses was halted from November 5, 2008 through June 27, 2013 (though existing same-sex marriages continued to be valid) due to the passage of Proposition 8—a state constitutional amendment barring same-sex marriages. The granting of same-sex marriages recommenced following the United States Supreme Court decision in Hollingsworth v. Perry, which restored the effect of a federal district court ruling that overturned Proposition 8 as unconstitutional.

On August 4, 2010, United States District Court Chief Judge Vaughn Walker declared Proposition 8 a violation of the Due Process and Equal Protection clauses of the U.S. Constitution in Perry v. Schwarzenegger, a decision upheld by the Ninth Circuit Court of Appeals on February 7, 2012. The case, known as Perry v. Brown in the Ninth Circuit, was appealed to the U.S. Supreme Court on July 31, 2012. The case was granted review as Hollingsworth v. Perry on December 7, 2012 and a decision was issued on June 26, 2013. The Court decided that the official sponsors of Proposition 8 did not have legal standing to appeal the district court decision when the state's public officials refused to do so. The judgment of the Ninth Circuit was vacated and the case was returned to that Court with instructions to dismiss the Prop 8 sponsors' appeal. On June 28, 2013, a stay of effect was removed from the federal district court decision and same-sex marriages were able to resume. Same-sex couples began marrying later that day.Before the passage of Proposition 8, California was only the second U.S. state (after Massachusetts) to allow same-sex marriage. Those marriages granted under the laws of other state governments, foreign and domestic, were legally recognized and retained state-level rights since 2008.