New York, New York - Carlos Alcaraz defeated Casper Ruud to win his first grand slam title at the US Open and become the youngest man ever to be ranked world number one.

Alcaraz and Ruud went into the match with both bidding for a first slam title and to make it to the top the rankings.

It was the Spanish teenager who came out on top, winning 6-4, 2-6, 7-6 (7-1), 6-3 in front of a jubilant crowd.

The 19-year-old is more than a year younger than Lleyton Hewitt was when he topped the standings in 2001.

The Australian's pre-eminence in the sport proved short-lived as first Roger Federer and then Rafael Nadal ascended to the top of the game, but in the week where King Charles assumed sovereignty, tennis appears to have crowned a new king.

It is only a year since Alcaraz burst into the spotlight by reaching the quarter-finals at Flushing Meadows but his talent was already well known within the sport, and he has climbed the rankings at warp speed.

He showed that he was ready to win the biggest titles by lifting Masters trophies in Miami and Madrid, where he beat Nadal and Novak Djokovic back to back, and has proved himself to be a complete player despite his tender years.

Alcaraz has also shown remarkable powers of physical endurance, recovering from three successive five-set matches, two of which finished past 2:00 AM.

No one has ever spent longer on court during a grand slam. At times the teen athlete appeared physically and mentally weary during the final, but Ruud, who was heavily beaten by Nadal in his maiden slam final at the French Open, could not find the killer blow.

The match was played under the roof on Arthur Ashe Stadium on a rainy day in New York, and Alcaraz moved into an early lead with a break in the third game.

Ruud sportingly gave his opponent a point after the umpire missed a double bounce, but Alcaraz did not really need the help as he clinched the first set.

He then forced a break point at 2-2 in the second set, but Ruud saved it. From there, the contest turned.

There were several of the all-court rallies that Alcaraz has made a habit of this tournament, and on one of them in the next game, Ruud made the breakthrough, celebrating exuberantly.

He then made it four games in a row as Alcaraz's energy dipped. The teenager broke early in the third but then handed it back with a tired-looking backhand into the net. For much of the rest of the set, Alcaraz was hanging on.

Ruud brought up two set points at 5-6, but Alcaraz bravely saved both with forays to the net. He found the perfect time to win his first tie-break of the tournament, albeit with a lot of help from his opponent.

Alcaraz was now right on his toes again, and pressure paid off when he broke through to lead 4-2 in the fourth set before serving out his historic triumph.

The Spaniard becomes the youngest slam champion since Nadal won his first French Open title 17 years ago, and the youngest at the US Open since Pete Sampras in 1990, while this was the second youngest men's final of the open era.