"Today is a historic day, our country has approved same-sex marriage, one more step forward in terms of justice, in terms of equality, recognising that love is love," Minister of Social Development Karla Rubilar said after the vote.

Chile's Senate and lower house of parliament both voted heavily in favour of the bill on Tuesday, which had been partially approved in November before the Senate sent it back to a committee for clarification.

President Sebastian Pinera, who will leave office in March, has backed the bill and is expected to sign it into law.

The vote culminates a process that began in 2017, when the first bill was introduced, backed by then-president Michelle Bachelet.

Chile is now poised to join more than 20 countries globally with legal same-sex marriage, including fellow Latin American nations Argentina, Brazil, Colombia, Costa Rica and Uruguay.

"It is hard to believe that today we are taking this step," said Rolando Jimenez from LGBT rights group Movilh, one of the major backers of the bill having helped spearhead Chile's push to legalise same-sex marriage for more than a decade.

Chile will elect a new president on December 19, choosing between progressive Gabriel Boric and social conservative Jose Antonio Kast, a practising Catholic.

The two offer wildly different visions for the country's future.

Chile has long had a deeply conservative reputation, but a strong majority of Chileans now support same-sex marriage and have shown signs of moving left on social and cultural issues.

Civil unions have been permitted in Chile since 2015, which affords same-sex partners many but not all the benefits of married couples, including the right to adoption.

The law, which will come into effect 90 days after it is published in the Official Gazette, was cheered by rights groups and couples, opening the door for both parents in a same-sex couple to receive full legal recognition.

"This is cause for all Chilean society to celebrate," said Isabel Amor, executive director of equality group Iguales.

"Not only will people who have a same-sex relationship be able to marry, but hundreds of children and adolescents will get recognition for their two mothers or two fathers."

Australian Associated Press