Warren Entsch became the first Coalition MP to introduce the bill, despite the fact that it is highly unlikely to go be put to vote before the next election, ABC reported.
"The main purpose of this bill is not a complex one, it is to give same-sex couples in Australia the same right to marry the person they love as that which is currently only granted by law to heterosexual couples," Entsch told the parliament
"This bill is designed to promote an inclusive Australia, not a divided one."
However, the Australian government's official position is that marriage should only be between a man and a woman.
Prime Minister Tony Abbott has denied government MPs a free vote on any bill legalising same-sex marriage.
Australia's Marriage Act limits marriage to a union of a man and a woman.
Earlier, Abbott said the matter should be "put to the people" in a non-binding plebiscite after the next general election, due in 2016.