Australia’s Parliament voted overwhelmingly to legalize same-sex marriage on Thursday, overcoming years of conservative resistance to enact change that the public had made clear that it wanted.

The final approval in the House of Representatives, with just four votes against the bill, came three weeks after a national referendum showed strong public support for gay marriage. The Senate passed the legislation last week.

The new law expands on earlier legislation that provided equality to same-sex couples in areas like government benefits, employment and taxes, and it changes the definition of marriage from “the union of a man and a woman” to “the union of two people.” It automatically recognizes same-sex marriages from other countries.

Gay rights advocates praised the landmark vote even as they said it was long overdue. In a country where there had been 22 unsuccessful attempts in Parliament to legalize same-sex marriage since 2004, they said, the law should be seen as the triumph of a democracy learning to live up to its values.

A handful of lawmakers tried to add amendments that they said were meant to safeguard religious freedoms for opponents of same-sex marriage, but their efforts failed. Mr. Turnbull noted that nothing in the legislation requires ministers or other celebrants to oversee weddings of gay couples or threatens the charity status of religious groups that oppose same-sex marriage, two concerns the lawmakers had raised.

The final debate in the House of Representatives, which lasted four days, featured more than 100 speakers.

On the first day, there was a marriage proposal: Tim Wilson, a gay member of Parliament with the center-right Liberal Party, spoke of the struggles he and his partner, Ryan Bolger, had encountered as a couple, before choking up, finding him in the public gallery and asking: “Ryan Patrick Bolger, will you marry me?”

The answer came loud and clear — “yes” — as did public congratulations from the deputy speaker, Rob Mitchell. Read more via New York Times