Cheered on by more than 25,000 singing fans at Auckland's Eden Park, the Tonga Invitational XIII inflicted the Kangaroos' first loss to a Tier 2 side and continued their historic run of wins after beating Great Britain last week.
The match was the last in a blockbuster international triple-header with Fiji thrashing Samoa 44-18 and New Zealand winning a tight encounter 12-8 over the Great Britain Lions in the early games.
But neither of those fixtures met the level of excitement of the Kau To'a v Kangaroos match up.
The first quarter of the match was full of intense defence and it took 21 minutes for a team to score, in the form of Tongan fullback Will Hopoate, who scooted over for a try converted by Kotoni Staggs.
Australia then looked to right the ship with two quick tries to Jack Wighton and Paul Vaughan and took a 12-6 lead into the break.
But instead of the heavy favourites continuing their momentum into the second half, it was the Tongans who took the impetus through tries to Michael Jennings and a typically robust 54th minute-score for Tevita Pangai Junior.
Cheered on by a sea of red, the Invitational XIII held on to humble the Australian Kangaroos, who comprehensively beat New Zealand last week.
Co-captains Jason Taumalolo and Siosiua Taukeiaho both paid tribute to their fans after their victory.
Taukeiaho indicated there had been a lot of uncertainty this year, much of it coming from a long-running dispute between coach Kristian Woolf and the local Tonga National Rugby League, and the team were not even sure if they would get to play a game.
However that all appears to be in the past now, with the historic and impressive victory on Eden Park.
Taumalolo said the fans were the reason the players had made many sacrifices to represent their island nation.
It was Taumalolo who led a group of high-profile players to commit to represent Tonga before the 2017 World Cup, an event which saw the team reach unprecedented levels of success and support, including a first victory over New Zealand and a place in the semi-finals.
Australian captain Boyd Cordner congratulated the Tongan team, saying they were too good on the night.
Despite the loss, Cordner's team still won the six-team Oceania Cup on points differential.