France could follow suit within days, after the Senate approved a bill last week, returning it to the lower National Assembly where debate resumed on Wednesday.
The move has been divisive in both countries, with opponents saying their governments should have put the matter to a referendum rather than pass laws.
The campaign in France saw hundreds of thousands of protestors take to the streets of Paris in January and March, and smaller protests took place on Wednesday, with police detaining at least 11 people after scuffles.
In New Zealand lawmakers were presented with a petition signed by 50,000 people opposed to the change. A post-vote New Zealand Herald online poll found respondents remain evenly divided, 44 percent each way, for and against the measure.
Although only 13 countries around the world have now legalized marriage between partners of the same sex at a national level since the Netherlands became the first to do so 12 years ago, the momentum appears to be picking up. Nine of the 13 have taken the step in the last four years.
When the New Zealand bill was first introduced in parliament last July, the sponsoring lawmaker cited President Obama’s public endorsement of same-sex marriage two months earlier as having added weight to the growing worldwide drive.
On Thursday the New Zealand decision was in turn being invoked in nearby Australia, where advocates called it a “game changer” in their own campaign to change the laws there.
Australian same-sex marriage proponents were frustrated last September by a parliamentary vote easily defeating a bill that would have allowed homosexuals and lesbians to marry.
Significantly, Australian Prime Minister Julia Gillard of the center-left Labor Party and center-right opposition leader Tony Abbott both opposed the bill. (By contrast, New Zealand’s center-right Prime Minister John Key voted in favor of the legislation on Wednesday.)
The New Zealand law does not include a residency requirement, so Australian same-sex couples could make the short trip and exchange vows there.
The Australian Marriage Equality lobby group says more than 1,000 couples have already indicated in a survey that they plan to marry in New Zealand as soon as possible.
“With marriage equality now just three hours away by plane, those Australian same-sex couples who are tired of waiting will marry in New Zealand instead,” said the group’s national convener, Rodney Croome.
Europe has led the way in the same-sex marriage push, and France is set to become ninth European nation to legalize it. On other continents proponents of traditional marriage lost their battles in Canada in 2005, South Africa in 2006 and Argentina in 2010. (Lawmakers in Uruguay passed a same-sex marriage bill last Friday and the president is expected to sign it soon.)
Although New Zealand is first in the Asia-Pacific to join the list no country in Asia-proper has yet done so.
In some Asian countries homosexuality remains outlawed. Homosexual acts are capital offenses in Iran, Saudi Arabia and Yemen, while Malaysia, Bangladesh and Papua New Guinea are among those where it is a crime punishable by imprisonment of 10 years or more.
The Asian country to first take steps towards redefining marriage was Nepal, where same-sex marriage was to have been included in a new constitution due to have been completed by May last year. But the drafting deadline was missed over political differences and an ensuing constitutional and political crisis has yet to be resolved.
In Vietnam, a law passed in 2000 outlawed same-sex marriage, but the Justice Ministry last year began calling for public submissions on the issue. On Monday the Thanh Nien Daily, an organ of the Communist Party youth league, reported that the Health Ministry plans to propose that same-sex marriage be legalized immediately.