The 18-year-old, ranked 118, thrashed the 38th best player in the world Magda Linette 6-1 6-1 in the second round of the Hobart International on Wednesday.
It was the best win by ranking of Joint's burgeoning career, topping Tuesday's round one straight-sets victory over world No.53 Olga Danilovic.
Joint, who surged up the rankings last year after being 773rd at the end of 2023, had too much power for the fourth seed Linette in a 61-minute demolition.
She is set to play her first Australian Open via a wildcard and is the second-highest ranked teenager in the world behind Russian 17-year-old and No.15 Mirra Andreeva.
And is coming off a second round showing in Brisbane last week where she took a set off two-time grand slam winner Victoria Azarenka.
Joint said the win over Linette, who is 14 years her senior, was the best of her career.
"I feel really good. I've played two really great matches (in Hobart) so far and I want to keep going," she said.
"I like being the underdog and have been trying to keep the pressure off myself.
"I really like that the season starts in Australia. The home crowd support is really special."
US-born Joint switched allegiances in 2023 to Australia, where her squash coach father hails from.
After two big upsets, Maya Joint will meet Sofia Kenin next in the Hobart International. (Lukas Coch/AAP PHOTOS)
She recorded her first WTA tour win at the 2024 US Open, where she progressed through qualifying and beat veteran Laura Siegemund in the first round.
Joint will meet Sofia Kenin on Thursday for a place in Hobart's final four after the 2020 Australian Open champion got past Anna Blinkova 6-2 3-6 6-2.
Kenin, who made the Hobart semi-finals in 2023 and lifted the trophy in 2019, said she was taking the tournament match-by-match.
"I'm very happy with the win. It definitely wasn't easy ... but I was able to battle through," she said.
Joint is the sole Australian remaining in the Hobart singles field after Daria Saville was knocked out by third seed Amanda Anisimova in the opening round.
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