The women's decider was locked 12-12 at fulltime, and it took until the first passage of extra time for Kelly Brazier to run length of field to gift New Zealand the gold 17-12.
The Australians, who had won the first Olympic gold medal in Rio in 2016 and dominated this season's women's sevens series, had been heavy favourites heading into the final between the trans-Tasman rivals.
"I thought "I'm out the front, I may as well not help anyone", so I got out there", she said.
The Canadian women's rugby sevens team will be playing for a bronze medal after a 33-7 loss to Australia.
Speaking of the intense rivalry with Australia, New Zealand's Theresa Fitzpatrick said: "They are our biggest competition and we are just as skilled, the skill level is high for both teams, it's just about heart".
"Nullifying her, that means somebody else is going to be exposed as well everyone has to do their job individually, make one-on-one tackles and it's a attractive day for running rugby so I expect a lot of that out there".
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Paul Georges, union president, said the response from teachers and paraprofessionals has been very positive. Students and teachers will cheer her on and take turns running by her side throughout the day and night.
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Poirier starts attacking the midsection of Gaethje with punches, Gaethje rocks a winging Poirier witha counter right hook.
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Charles Da'Vall Grice of England beat Johnson to the fourth position by a fraction of a second with a time of 3:37.43. Vipin Kashana, the other Indian in the fray, took the fifth spot with an attempt of 77.87m.
Brazier's lung-bursting effort, however, would have been in vain had Michaela Blyde, who scored one of New Zealand's two tries in the first half, not produced two sensational cover tackles as Australia pressed in the second half.
"We're devastated. you can't fault the effort we put in but we don't like losing", Walsh said.
"They were under some severe pressure there but they just looked after the ball and sooner or later knew someone was going to crack".
An Emma Tonegato hat-trick has put Australian Women in the gold medal match in resounding fashion.
New Zealand's Regan Ware makes a break against Fiji.
The Aussies will face the victor of New Zealand's clash with England at 2:42pm AEST.
England stormed back from 0-14 down at half-time with skipper Tom Mitchell scoring the winning try to take the bronze medal 21-14 over South Africa.