The private member's bill comes amid heated debate among government MPs about whether to change the law or put the matter to a plebiscite.
The 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.
The bill allows couples, regardless of "sex, sexual orientation, gender identity or intersex status" to marry.
Australia's Marriage Act limits marriage to a union of a man and a woman.
The bill was introduced by government backbencher Warren Entsch, one of several government backbenchers who plan to defy Mr Abbott by crossing the floor of the parliament to vote in favour of marriage equality.
The ban on a free vote for government MPs means it is likely to fail.
Mr Abbott has said the matter should be "put to the people" in a non-binding plebiscite after the next general election, due in 2016.
Meanwhile, cross bench senators have backed an Australian Greens bill calling for a gay marriage plebiscite before the election.
In an impassioned speech, Mr Entsch spoke of how his bill, which has cross-party support, was designed to promote a more inclusive Australia.
"Being gay is not a lifestyle choice," the Queensland MP told the parliament.
"This bill does not create different classes of marriage," he said.
"A divided nation is what we will be if we continue to allow discrimination in relation to marriage on the basis of a person's sexuality."
A controversial bill to legalise same-sex marriage has been introduced to the Australian parliament.