The Wallabies secured at least third spot in Pool C but must wait for Fiji's last match to see if they make Finals.
The Wallabies have recorded a bonus-point victory over Portugal in their final pool game at the Rugby World Cup, keeping their hopes alive of progressing to the Quarter-Finals.
The 34-14 victory means the Wallabies now need Portugal to beat Fiji by eight points or more in their final pool match next Monday morning (AEDT) in Toulouse to make it through to the knockout phase.
The win was built off a strong first half, the Wallabies scoring three tries in a seven-minute period.
Fraser McReight's try sealed the win after the break, while Marika Koroibete crossed for a well-deserved try late in front of over 40,000 fans.
"We're still alive. That was the aim of the day," said Wallabies coach Eddie Jones.
"For a young team down to 13 men we showed plenty of courage and fought hard.
“We've done that all season, sometimes the results haven't been in our favour... It's a real credit to them.
“You look at the experience of our players out there, we're averaging less than 20 caps."
Following an early penalty goal to the Wallabies, ‘Os Lobos’ stunned the Australians when they went over out wide for the first try of the match, Pedro Bettencourt diving over to the delight of the Saint Etienne crowd.
Bettencourt’s heroics were short-lived, with the centre sitting down for ten after a high tackle on Izaia Perese.
This allowed the Australians to settle into the game, and it was prop Angus Bell who delivered a clinical spell of play to spark the Wallabies.
It started with a great run off a lineout just inside Portugal’s 22, followed by Rob Valetini popping the offload for Richie Arnold to score.
He then won a turnover that allowed Dave Porecki to barge over from a rolling maul, helped by a perfect kick from Ben Donaldson.
The loosehead finished it off with a barge over from close for his first try in gold to give Australia a commanding 24-7 lead by the time Bettencourt returned from the bin in the 26th minute.
Portugal nearly scored before the break, only to be stopped by a flying Andrew Kellaway bundling Nicolas Martins into touch.
Nawaqanitwase’s basketball pass to Fraser McReight shortly after the break helped secure the all-important bonus point but the Australians didn’t make life easy for themselves.
They were reduced to 13 when Matt Faessler was sent for ten minutes on the sideline for collapsing a maul, before Samu Kerevi followed him for a raised elbow in a carry.
The numbers advantage gave Portugal an opportunity to display more of their free-flowing and frenetic style, with the Wallabies showing determination to hold out Portugal.
Eventually, the extra players proved too much and Rafael Simoes crashed over off the back of a scrum.
Kerevi returned to the field with a point to prove, bursting through the line with a great run and winger Marika Koroibete – who delivered a series of brutal hits throughout the game – following it up to score a well-earned try to close out the game for the Wallabies.
[Tries: Arnold, Porecki, Bell, McReight, Koroibete; Cons: Donaldson 3; Pen: Donaldson] Portugal 14 [Tries: Bettencourt, Simoes; Cons: Marques 2]
Yellow cards: Pedro Bettencourt (Portugal, 15′ – foul play, high tackle); Matt Faessler (Portugal, 60′ – cynical play, collapsing the maul); Samu Kerevi (Australia, 62′ – foul play, dangerous hand-off)
Australia: 15 Andrew Kellaway, 14 Mark Nawaqanitawase, 13 Izaia Perese, 12 Lalakai Foketi, 11 Marika Koroibete, 10 Ben Donaldson, 9 Tate McDermott, 8 Rob Valetini, 7 Fraser McReight, 6 Tom Hooper, 5 Richie Arnold, 4 Nick Frost, 3 James Slipper, 2 David Porecki (captain), 1 Angus Bell.
Replacements: 16 Matt Faessler, 17 Blake Schoupp, 18 Pone Fa’amausili, 19 Rob Leota, 20 Josh Kemeny, 21 Issak Fines-Leleiwasa, 22 Samu Kerevi, 23 Suliasi Vunivalu.
Portugal: 15 Nuno Sousa Guedes, 14 Raffaele Storti, 13 Pedro Bettencourt, 12 Tomás Appleton (captain), 11 Rodrigo Marta, 10 Jerónimo Portela, 9 Samuel Marques, 8 Thibault de Freitas, 7 Nicolas Martins, 6 David Wallis, 5 Martim Belo, 4 José Madeira, 3 Diogo Hasse Ferreira, 2 Mike Tadjer, 1 David Costa.
Replacements: 16 Francisco Fernandes, 17 Duarte Diniz, 18 Francisco Bruno, 19 Steevy Cerqueira, 20 Rafael Simoes, 21 Joao Belo, 22 Joris Moura, 23 Manuel Cardoso Pinto.
Referee: Nika Amashukeli (Georgia)
Assistant Referees: Mathieu Raynal (France) & Andrea Piardi (Italy)
TMO: Joy Neville (England)