Mike Gibson (1967 in Sydney) and Ollie Campbell (1979 in Brisbane and Sydney) were the only previous number 10s to achieve the feat, giving a sense of how remarkable the accomplishment is.
Sexton landed two penalties and a drop goal to steer Ireland into a 9-6 lead at Eden Park, before O'Gara assumed the place-kicking duties and knocked over a brace of clinching penalties.
It was the St. Mary's College clubman's 21st appearance for Ireland, but only his second Rugby World Cup match and he showed commendable poise, even sidestepping past his former Leinster team-mate Rocky Elsom at one stage.
There was a huge Irish presence amongst the 58,678-strong crowd and the New Zealanders present also got behind the men in green in their bid to upset the odds.
Praising the fans for the support they provided, Sexton told RTÉ Sport: "We had a day off during the week, popped into town and there were Irish people everywhere. We knew even more were coming out yesterday and today, a lot of the parents and families arrived.
"The amount of people that turned up, we really just wanted to put in a performance for them. It will live long in all our memories as players. I'll remember forever the amount of people that turned up.
"The noise, at times, felt like we were in the Aviva (Stadium). It made the day even more special for us."
He added: "The way Paul O'Connell spoke last night...and Jerry Flannery presented us with our jerseys, he's going to play no more part in the World Cup, he's going home.
"The emotion that Jerry had last night just showed what the jersey meant to us and we wanted to put that out on the pitch today."
Such was the strength of the Irish defence, it was the first match Australia failed to score a try in since they lost to New Zealand back in September 2009.
The losing margin also equalled the Wallabies' heaviest defeat in a World Cup game - they were beaten 27-18 by South Africa in a 1995 pool fixture.
"We did have to dig deep. Australia are a quality team, at times they put us under pressure. If you give them time and space, they will put you under pressure.
"I thought we shut them down quite well, they had a couple of opportunities that they didn't take and we had a couple of opportunities that we didn't take.
"The conditions were pretty tough. It was tough to play in, you've just got to keep the pressure on them and keep the ball in behind them."
Despite the historic result, Ireland's outlook for their final two Pool C ties remains the same. Sexton is sure they will stay grounded as they still have to secure qualification for the knockout stages and ideally as pool winners.
"We're halfway there in terms of getting out of our pool. We haven't looked past that stage," he added.
"We've got to regroup for Russia next week and then go again against Italy who I'm sure will be playing to get out of the pool.
It's wide open now, it'll probably come down to bonus points. We just need to regroup and get two more wins."
Follow the Ireland team in New Zealand on www.twitter.com/irfurugby.