Same-sex couples hurried to declare plans to tie the knot on Saturday as Australia’s new marriage equality law came into effect, with wedding registry offices holding special hours for the first day of legalised gay unions.

The historic bill finally legalising same-sex marriage came into effect barely 24 hours after its overwhelming passage through parliament.

Couples wanting to wed under the new law can lodge a notice to marry Saturday, but will have to wait a calendar month before exchanging vows, meaning the first weddings are expected on January 9.

"I put in an enquiry yesterday, didn’t expect to hear back from someone so quickly and they said ’oh, we are open specially today’, so we thought ’okay, let’s go and do it, let’s do it asap’," said Clare Jacobs, holding tight to her newly-official fiancee Valeria Ballantyne.

"I thought we would just come in and sign a form and it would just be a formality, but it’s actually quite emotional," added Ballantyne.

The legislation came after more than 60 percent of Australian voters backed marriage equality in a contentious three-month national postal vote.

To mark the historic moment, registry offices in some parts of the country exceptionally agreed to accept new marriage applications Saturday, when normally they are only open to conduct weddings.