The 21-year-old defeated Ons Jabeur 6-2 7-6 (5) in an hour and 50 minutes at Flushing Meadows to add her first hard-court major trophy to her two French Open successes.
Jabeur, playing in her second consecutive slam final after losing to Elena Rybakina at Wimbledon, threatened a comeback in the second set but Swiatek held firm to clinch it in a tie-break.
Her second victory at Roland Garros in June was part of a 37-match unbeaten run and it is fitting that, in the tournament where Serena Williams bowed out, Swiatek becomes the first woman since the American in 2014 to claim seven titles in a season.
She is a very different character to Williams and has an understated presence on court but possesses an inner belief that has now carried her to straight-sets victories in her last 10 finals.
Jabeur went into the match full of confidence after a straightforward semi-final against Caroline Garcia and believing she had learned from her Wimbledon defeat.
Bidding to become the first African and Arab woman to win a grand slam title, Jabeur leads the tour in terms of match wins since the start of 2021 – now one ahead of Swiatek – and will rise to world number two on Monday.
But she had lost her only previous match this year to Swiatek 6-2 6-2 in the final in Rome in the spring and made a very nervous start.
While the top seed was swinging freely, barely missing a first serve and making every return, Jabeur was struggling with all those things and won only two points in the first three games.
She steadied herself and broke Swiatek back with four clean winners but the tide quickly turned again.
Jabeur is at her best when she can express her vibrant personality, teasing opponents with drop shots and clever touches at the net, but the pace and accuracy of Swiatek’s ball was keeping her pinned behind the baseline.
The drop shots she did try felt like desperate moves and mostly landed in the net, while her serve, which has been a strong weapon this fortnight, was not working either.
Remarkably, Swiatek breaks serve in more than half of the return games she plays and Jabeur’s frustration increased as the Pole moved ahead at the start of the second set.
It appeared little more than a glimmer of hope when Jabeur saved break points at 3-0. But, with Swiatek seemingly unsettled by repeated shouts from the crowd, the Pole’s level began to drop.
Jabeur fought back to level at 4-4 and, had she taken any of the three break points she created in the next game, the contest might well have gone to a decider.
But Swiatek held on and, despite missing a match point at 5-6, converted her second chance in the tie-break.