Mexico’s most populous state, State of Mexico, overwhelmingly voted to legalise same-sex marriage on 11 October.
It becomes the 29th of the country’s 32 states to do so after being passed by 50 votes in favour to 16 against.
“Equal marriage is a public institution, whereby two people freely decide to share a life,” the state’s legislative body wrote on Twitter.
State of Mexico is home to around 17 million people, making it the country’s most populous state at a size five times the population of Uruguay.
“Today, by becoming the 29th state to approve equal marriage, we will be reducing inequality, and letting the country know that in the State of Mexico we do not leave anybody behind,” said state legislator Paola Jiménez.
Mexico City was the first part of the country to legalise same-sex marriage more than a decade ago in 2009, with the recent vote following the states of Sonora and Sinaloa.
Tamaulipas, Tabasco and Guerrero are now the only three Mexican states to not have such laws in place.