Supporters of the law, who had filled the public seats in the legislative building, erupted in celebration when the results were announced. The bill received the backing of 71 of the 92 members of the Chamber of Deputies present.
"We are living a historic moment," said Federico Grana, a leader of the Black Sheep Collective, a gay rights group that drafted the proposal. "In terms of the steps needed, we calculate that the first gay couples should be getting married 90 days after the promulgation of the law, or in the middle of July."
The "marriage equality project," as it is called, was already approved by ample majorities in both legislative houses, but senators made some changes that required a final vote by the deputies. Among them: Gay and lesbian foreigners will now be allowed to come to Uruguay to marry, just as heterosexual couples can, said Michelle Suarez of the Black Sheep Collective.
President Jose Mujica, whose governing Broad Front majority backed the law, is expected to put it into effect within 10 days.
Nationalist Sen. Gerardo Amarilla opposed the law, saying it "debases the institution of marriage" and affects the family, especially in its "role in procreation."
The vote makes Uruguay the third country in the Americas after Canada and Argentina to eliminate laws making marriage, adoption and other family rights exclusive to heterosexuals. In all, 12 nations around the world now have taken this step.
While some countries have carved out new territory for gay and lesbian couples without affecting heterosexual marrieds, Uruguay is creating a single set of rules for all people, gay or straight. Instead of the words "husband and wife" in marriage contracts, it refers to the gender-neutral "contracting parties."
All couples will get to decide which parent's surname comes first when they have children. All couples can adopt, or undergo in-vitro fertilization procedures.
The legislation also updates divorce laws in Uruguay, which in 1912 gave women only the right to unilaterally renounce their wedding vows as a sort of equalizer to male power. Now either spouse will be able to unilaterally request a divorce and get one. The law also raises the age when people can legally marry from 12 years old for girls and 14 for boys to 16 for both genders.
Outside congress, gay couples holding hands, transvestites and transgender couples jumped in celebration when the result was announced. People in costumes carrying Uruguayan and rainbow flags danced to electronic music.
"I have all the rights and obligations of everyone else. I pay my taxes and fulfill my responsibilities, why would I be discriminated against?" said Roberto Acosta, a 62-year-old retired gay man.
Mujica, who spent more than a decade in prison for his actions as a leftist guerrilla in the 1970s and still lives on a ramshackle flower farm in a poor neighborhood on the edge of Uruguay's capital, has pushed for a series of liberal laws recently. Congress agreed to decriminalize abortion, but Mujica had to suspend an effort to put the government in charge of the marijuana business, saying society has to reach consensus on that idea first.
Uruguay's Roman Catholic Church asked lawmakers to vote their conscience and challenged the label of "marriage equality" as a false pretext, saying it's "not justice but an inconsistent assimilation that will only further weaken marriage."