Liberal MP Tim Wilson, 37, was emotional as he spoke during the debate on Monday, as he stood and thanked his long-term partner, primary school teacher Ryan Bolger, 33, for supporting him.
While they already considered themselves engaged, the rings they wore on their left hands, he said, were their answers to a question that they once could not ask. "So there's only one thing left to do".
"In my first speech I defined our bond by the ring that sits on both of our left hands, and they are the answer to a question we can not ask", an emotional Wilson said, referring to the first time he addressed the Parliament a year ago.
Bolger nodded and mouthed the word "YES" to a thunderous applause from on-lookers.
However there may be a number of 'religious freedoms' included in the bill, which make it legal for service providers to reject gay couples.
A marriage equality bill that passed the senate last week is being debated in the lower house, where it is expected to pass this week.
"I should let Hansard note to record that that was a 'yes, ' a resounding yes", said Mitchell.
Officials from the House of Representatives noted on Twitter that he was also the first member of Parliament to ever propose in the chamber.
About 77 MPs are due to deliver speeches on the Bill before it is voted, likely on Wednesday evening or Thursday morning.
If the House of Representatives supported such an amendment, then the altered bill would have to return to the Senate for ratification, delaying the reform.
But a speech from Prime Minister Malcolm Turnbull had people up in arms.
Legalizing same-sex marriage is on the home stretch in Australia.
The bill was the 21st same-sex marriage bill to be brought before the Senate, and the first to succeed.
It's the first time a marriage proposal has been made during a parliamentary sitting.
She continued: "Australians did their job and overwhelmingly said YES to marriage equality in one of the biggest political mandates in Australian history".