With the win, sixth seed Gauff became the first American to win a US Open title since Sloane Stephens in 2017.
Gauff fed off an adoring home crowd as she mounted a terrific second set fight back and kept the momentum up through the end of the battle, before she fell to the court on Arthur Ashe Stadium after clinching the title with a backhand winner.
Sabalenka had a superb start but could not keep the momentum going as unforced errors piled up and she closed her 2023 Grand Slam run, which included an Australian Open title and semi-finals at Roland Garros and Wimbledon, on a disappointing note.
There were signs of nervousness from both players early on, as Gauff made a pair of unforced errors to help Sabalenka to a break in the opening game and the Belarusian dropped serve in the fourth game with two double faults and an unforced error.
The crowd urged on Gauff, the first American teenager to reach the US Open singles final since Serena Williams in 2001.
But Sabalenka blocked out the noise and used her mighty forehand to convert on a break-point chance in the fifth game.
The Belarusian was helped to another break in the seventh as Gauff double-faulted and made two more costly forehand mistakes.
Sabalenka, who will take over as world number one in the new rankings, had ended Gauff's run at Indian Wells earlier this year but told reporters this week she expected a “different player” in Saturday’s final.
She got just that in the second set, as the American showed new resolve when she fended off a pair of break points in the first game and flipped the script.
What was once a lopsided affair turned into a battle as Gauff increased her intensity, sending Sabalenka scrambling around the court in the fourth game before the Belarusian dropped her serve with a double fault.
Gauff produced an overhead smash to break in the opening game of the third set and converted another in the third game.
Sabalenka took a medical timeout after the fifth game, consulting a physio for an apparent issue with her left thigh, but did not appear worse off as broke in the next game.
If Gauff was rattled, however, she did not show it, winning a 20-shot rally before breaking back in the seventh game and soaking up the adoration of the crowd at the major she grew up watching as she clinched the title.
The 2022 Roland Garros runner-up burst into tears and embraced her parents in the stands as she took in the moment.
