The 17-year-old qualifier from Atlanta, who was held hostage at the age of seven and whose father who was dug out of the rubble of the 2010 Haiti earthquake, announced herself on the world stage with a stunning 5-7 6-4 6-4 victory.
The 11th seeded Australian, the 2011 champion in New York, looked to have control of the match when she led 4-2 in the second set.
Duval held her nerve, though, to serve out for the win in two hours and 39 minutes on Louis Armstrong Stadium.
"I'm very goofy off the court," Duval said after the first-round win. "I think I'm very much a child at heart. But on the court you have to be a warrior because that's just the sport we are in."
Duval's father, Jean-Maurice, was courtside at the Louis Armstrong Stadium when his daughter pulled off the first major upset of the tournament.
Three years ago, his legs were broken, his left arm shattered and seven fractured ribs had punctured his lung after the catastrophic earthquake on the Caribbean island.
A tennis connection played an instrumental part in his recovery with an Atlanta family connected with Duval's club paying to airlift him to a Florida hospital.
That only happened after his passport was also dug out of the rubble and the role of the Kitchen family in her father's rescue was not forgotten by Duval in the biggest moment of her fledgling career.
"Emotionally it was hard at first," Duval said. "But he's as happy as he's ever been. He had a couple of surgeries that helped take the pain away.
"We're just so happy that, you know, he's in a good state of mind right now. He's here with us, so it's incredible. We're forever grateful to the Kitchens.
"If it wasn't for them, my dad definitely wouldn't be here today. Not everyone just pays $30,000 to fly a helicopter to save someone.
"Great story. They're amazing people. I mean, they're angels. We could not have found better people."
It was also in Haiti that Duval, then seven, and her cousins were held hostage at her home by gun-wielding thieves a decade ago.
"It's not a good memory, so I try to forget as much as I can about it," she said. "I don't remember too much of it anymore, which is great."
Duval also struggled to recall the decisive moment of her victory over Stosur, who beat the might of Serena Williams to win the title at Flushing Meadows only two years ago.
"A lot of different emotions," she said. "Mostly happiness.
It was incredible. I don't even remember match point.
"I guess I was really happy. You could tell by all the jumping I did."
Duval, who will meet Slovakia's Daniela Hantuchova in the second round, said part of her career ambition was to join the likes of Sloane Stephens in restoring the United States to its position as the dominant power in world tennis.
"We're obviously trying to make American tennis become what it used to be," she said.
"We're all working towards the same goal. We're all a tight-knit group. Helping each other is important. I think we're on an amazing path."
World number 11 Stosur paid tribute to Duval's powerful groundstrokes but also blamed herself for the defeat after hitting 56 unforced errors.
"I think she played well, but I think I certainly helped her along the way," the Australian said.