The first crop of legal gay weddings will take place around the country on Tuesday, a month after Australia became the 26th country to allow same-sex marriage.

While a handful of special-case ceremonies have already taken place, most couples have had to see out the statutory one month waiting period until they can actually tie the knot. The law officially changed on December 9, making Tuesday, January 9 the first day for vows to be exchanged between husband and husband, wife and wife.

Preparations were underway for weddings in Sydney's Centennial Park, on the steps of the Western Australian Parliament and at an estate on the Tweed Coast, where Commonwealth Games athlete Craig Burns will wed his fiancee and fellow sprinter Luke Sullivan at the stroke of midnight.

"It'll be a special moment to know that we're a part of that and it's an awesome step forward for Australia," Mr Burns told the Mackay Daily Mercury. A few hours later at Perth's Court Hotel, a special public event will kick off as the clock strikes 12 with the wedding of a local teacher and nurse.