The first same-sex couples walked down the aisle in the Netherlands in 2001, with others following suit in Canada, South Africa, Belgium and Spain. Argentina was the first Latin American nation to legalize such marriages, in 2010. Other countries on the list are Denmark, Iceland, Norway, Portugal and Sweden.
Many countries remain split over the issue. A Brazilian court this week issued a directive removing a barrier that had limited same-sex marriage, but no bill has made it through Congress.
In the United States, the question went before the Supreme Court and justices are deliberating over the matter.
Twelve U.S. states and the District of Columbia have legalized same-sex marriage. On the other side, many states have specific laws blocking same-sex couples from legally marrying.