Same-sex adoption is the adoption of children by same-sex couples. It may take the form of a joint adoption by the couple, or of the adoption by one partner of the other's biological child (stepchild adoption).

Joint adoption by same-sex couples is permitted in 34 countries, most of the countries and territories that allow same-sex marriage, as well as in several countries and dependent territories that do not: namely Croatia, Israel, Liechtenstein, Bermuda and the Cayman Islands. (In some of the countries with marriage, legislation for adoption preceded that for marriage.) However, only stepchild adoption is permitted in Taiwan (though since 2022 there is court precedent for joint adoption), and not even that is allowed in Ecuador, which has a constitutional ban. Adoption is only permitted for same sex married couples in 21 of the 31 Mexican states and Mexico City, despite a Supreme Court ruling that requires states to allow it. Stepchild adoption is permitted for same-sex couples in a couple additional countries without same-sex marriage, namely Estonia and San Marino.

Given that constitutions and statutes usually do not address the adoption rights of LGBT persons, judicial decisions often determine whether they can serve as parents either individually or as couples. Opponents of adoption by same-sex couples have argued that LGBT parenting adversely affects children. However, research consistently shows that gay and lesbian parents are as fit and capable as heterosexual parents, and their children are as psychologically healthy and well-adjusted as those reared by heterosexual parents.

Same-sex parents pursuing adoption must also contend with social pressures to conform to heteronormative gender roles. The concept of gender role models is necessitated by the bureaucratic organization of foster care and adoption agencies, particularly in the United States.