The proposal now goes to the Senate, where the ruling coalition has enough votes for passage. President Jose Mujicaplans to sign it into law early next year.
The proposal, which passed the lower house of Congress by a wide margin Tuesday, would also let all couples, gay or straight, decide whose surname goes first when they name their children.
That breaks with a tradition that has held for centuries across Latin America, where in nearly every country, laws require people to give their children two last names, and the father's comes first.
"It's an issue that will generate confusion in a society that has forever taken the father's name. But these changes in society have to be accepted," said Deputy Anibal Gloodtdofsky of the right-wing Colorado Party, who told The Associated Press he plans to join the ruling Broad Front coalition and vote in favor on Tuesday.
The "Marriage Equality Law" also would replace Uruguay's 1912 divorce law, which gave only women, and not their husbands, the right to renounce marriage vows without cause. In the early 20th Century, Uruguay's lawmakers saw this as an equalizer, since men at the time held all the economic and social power in a marriage, historian Gerardo Caetano said.
The Roman Catholic Church is opposed to the proposal, but the church has little political influence in secular Uruguay.