WATCH: Alcaraz and Ruud faced off for a rematch of their Miami Open final, where Alcaraz triumphed in straight sets.

NEW YORK—Carlos Alcaraz comes of age in New York City, becoming the youngest US Open champion since Pete Sampras won his first major in 1990—and the seventh youngest in the Open Era—by edging out Casper Ruud, 6-4, 2-6, 7-6 (1), 6-3. Alcaraz is also set to become the youngest-ever ATP No. 1 when the rankings are updated on Monday.

The 19-year-old has looked like an inevitable Grand Slam winner since a breakout swing saw him win Masters 1000 titles in Miami and Madrid, and he erased disappointments at Roland Garros and Wimbledon with a physical two weeks of tennis in Flushing Meadows—following up a trio of late-night three-setters for a triumphant win over Ruud in three hours and 20 minutes on Arthur Ashe Stadium.

Facing off for a rematch of the Miami Open final, Ruud has looked far more comfortable on hard courts since surging up the ATP rankings on his beloved clay, reaching the semifinals at the Omnium Banque National ahead of his return to Flushing Meadows.

Though he had never been past the third round in four previous attempts, the 23-year-old held off an inspired Tommy Paul to reach the second week and scored statement wins over former Wimbledon finalist Matteo Berrettini and Olympic silver medalist Karen Khachanov to reach his second Slam final of the season.

While Ruud could boast more big-stage experience, Alcaraz has seemingly had destiny on his side since beating both Rafael Nadal and Novak Djokovic to win the Mutua Madrid Open in May, looking like an obvious successor to the Big 3 with his unique combination of offense, athleticism, touch, and variety.

His all-court game helped him through photo finishes against 2014 champion Marin Cilic, Jannik Sinner, and Frances Tiafoe to get him into what felt like an overdue first championship weekend.

Once there, he hit the ground running against Ruud, navigating a tense opening four games—during which he saved three break points—to emerge with the first break, carrying it through the first set as celebrities like Jerry Seinfeld, Anne Hathaway, and Zach Braff looked on.

Alcaraz showed no signs of physical fatigue in the early goings—repeatedly rushing the net to serve and volley—forcing the No. 5-seeded Ruud to raise his level in the second set. Capitalizing on some loose shots from the teenager, Ruud earned his first break of the match and nabbed a second to even things at one set apiece.

An early exchange of breaks to start the third made for dramatic viewing as the pair headed towards a tiebreaker: Ruud dug out of a difficult game at 4-4 only to see two set points go begging as Alcaraz served at 5-6.

The Norwegian’s hitherto clutch play suddenly went out the window, however, and Alcaraz won an undramatic Sudden Death thanks to a slew of unforced errors that put him a set away from his first major victory.

Energized by the lead, Alcaraz was quickly up a break in the fourth as the finish line drew closer, a deflated Ruud missing an overhead to give up break point. Ruud kept things close from there, opening up a 0-30 lead on the Alcaraz serve and putting down a love hold as he served to stay in the match, but Alcaraz would not be denied.

Shaking off an overhead miss and overly exuberant forehand, he converted his second championship point and dissolved into tears at the service line—embracing Ruud, now the new No. 2, at net.