More than 30 same-sex couples will say "I do" Monday when New Zealand becomes the first Asia-Pacific country and only the 14th in the world to legalise gay marriage.
The move has sparked a raft of competitions to set wedding firsts, but unease amongst the religious community.
American actor Jesse Tyler Ferguson, from the hit comedy "Modern Family" will be the guest of honour when Air New Zealand hosts a same-sex marriage on an early flight from Auckland to Queenstown.
Two radio stations are also vying to host the first same-sex wedding, with the ceremonies broadcast live during their breakfast programmes.
The first Australian couple to wed will be Paul McCarthy and Trent Kandler from New South Wales, who beat 300 other pairs to win a Tourism New Zealand competition.
Their wedding will not be legally recognised at home, but McCarthy said it was "both historically significant, and an important step in our personal lives".
About 1,000 same-sex couples in Australia have indicated that they plan to travel to New Zealand to marry, according to the Australian Marriage Equality lobby group.
The Department of Internal Affairs said Sunday same-sex couples had flocked to registry offices in recent weeks to pick up marriage licences and 31 couples had indicated they would be getting married on Monday, usually the least popular wedding day.
"They were really excited, congratulating each other and themselves that the law change had come into effect so they were able to marry," the registrar-general of marriages Jeff Montgomery told reporters.
There has also been overseas interest from Russia, the United States, Hong Kong, Britain, Singapore, Malaysia, Guyana and Belgium.
Established Christian churches, however, were uneasy about the new law with Roman Catholics opposed outright while Anglicans, Presbyterians, Methodists, and Baptists were split.
The Anglican Church asked its ministers to refrain from conducting same-sex weddings pending a report to its general synod next year.
Meanwhile, a new group has been formed calling for legalised multi-partner marriages.
A statement on the "Support legalised Polyamory in NZ" Facebook page said it wanted legal recognition of "responsible, adult, committed non-monogamy (plural marriage of any gender) marriage or union".