Spain is now the fourth country in the world to allow same-sex couples the same rights as married heterosexual couples. Canada approved gay marriages yesterday, while the Netherlands and Belgium legalised them in 2000 and 2003.
The Methodist church in Britain yesterday became the first big Christian denomination to offer the prospect of blessings services for same-sex couples.
The landmark ruling in Spain gives married gay couples equal rights to inheritance and allows them to adopt children. They will also be given the same rights as married heterosexual couples when getting divorced.
José Luis Rodríguez Zapatero's ruling Socialist government proposed the bill shortly after winning the election last year. On the day he was confirmed as prime minister, Mr Zapatero said he would fight discrimination against homosexuals.
During the debate before today's historic vote, Mr Zapatero acknowledged Spain was joining the growing numbers of countries legalising gay marriages.
"We are not the first, but I am sure we will not be the last," he told the chamber. "After us will come many countries, driven, ladies and gentlemen, by two unstoppable forces: freedom and equality."
The Roman Catholic church and conservative leaders fiercely opposed the bill, but that was always unlikely to stop it gaining support in the congress of deputies.
The bill was passed by 187 votes to 147. Four members refused to vote on the issue.
The senate, where conservatives have the majority, rejected the bill last week, but final say on legislation rests with the congress.
The church is so opposed to the bill it took the rare step of endorsing a rally in which hundreds of thousands, including 20 bishops, marched through Madrid protesting against the legislation on June 18.
Late last year, the spokesman for the Spanish bishops conference, Antonio Martínez Camino, said that allowing gay marriage was like "imposing a virus on society - something false that will have negative consequences for social life".
Gay rights groups welcomed today's vote and said the first gay marriages in Spain could take place as soon as 15 days after the law is published in Spain's official journal.
"This victory in Spain will make many other countries start the battle for equality because it is possible," said gay rights activist Beatriz Gimeno.
"If Spain, a Catholic and southern Mediterranean country with a short history of policies in protecting social freedoms can do it, it is perfectly possible that any other European country can do it."
During the 1939 to 1975 dictatorship of Francisco Franco, homosexuality, divorce and abortion were illegal. But since Franco's death the country has adopted some of the most liberal views in Europe.
