The Netherlands was the first country to legalize same-sex marriage in 2001. Since then, almost 40 other countries have followed suit.
You can see this in the chart, based on data from Pew Research. By 2025, same-sex marriage was legal in 39 countries.
Last year, two countries were added to the total. Thailand became the first country in Southeast Asia to legalize same-sex marriage, and a same-sex marriage bill also took effect in Liechtenstein.