The 19-year-old from Murcia is the youngest world number one in history after beating Norway’s Casper Ruud 6-4 2-6 7-6 6-3 in three hours and 20 minutes.
Fleet of feet and thunder of thighs, Alcaraz has gone from number 32 at the start of the year to the top of the rankings.
Alcaraz fell to the floor after earning the deciding point of the match – and the tournament
The 19-year-old faltered slightly in the second set, but proved too strong in the end
It’s Alcaraz’s first Grand Slam and more could be on the way if he continues
Alcaraz celebrates with his coach Juan Carlos Ferrero after winning the tournament
Carlos Alcaraz lifts the trophy at Arthur Ashe Stadium after winning the US Open
He emulates his coach, Juan Carlos Ferrero, but also Pete Sampras, who won the Open at the same age. Unlike Ferrero, he looks set to occupy the position for much longer than eight weeks.
A match full of great all-court rallies headed into the tiebreak when Rudd seemed to be reeling with the match at his mercy. A flurry of misses gave it to Alcaraz, who was starting to look physically weak and tired after his previous efforts in the tournament.
There was the odd flap as he served it, but he closed out the match with an unstoppable service winner.
Casper Ruud put in a valiant effort but ultimately couldn’t hold off his talented opponent
The Norwegian is now No.2 in the world after reaching finals in New York and France this year
Casper Ruud holds the runners-up trophy after falling to Alcaraz in four sets
It wasn’t long before Rude discovered he was the second favorite among the crowd.
Steady drizzle all day meant the roof would close and the first impact was to be caught in the roar that went up when the young Spaniard walked onto the pitch.
Not that the Arthur Ashe Stadium was unfriendly to the suave Norwegian, but there was clearly a desire to see history made by the teenager.
Both players were nervous and error-prone in the early stages, with breakpoints coming at both ends. It was also obvious that this race was going to feature some impressive recovery from two of the fastest athletes on tour.
Alcaraz broke for 2-1 when his deep return forced the Scandanavian into a backhand on the tramlines.
The two exchanged a hug after the grueling three hour and two minute match
Alcaraz is the youngest world No. 1 in tennis history and won’t turn 20 until May
If the Spaniard has a weakness, it’s that he still has a tendency to be tight and take the lead, but amid brilliant scrambles he held the advantage to claim the first set.
When he did it was, incredibly, the 65th consecutive match on tour in which he had won at least one set in a match.
The Spaniard lost some consistency in the second and at 2-3 was broken when Rudd came inside and hit a superb backhand lob. He looked in trouble when he broke again to lose the set, with the Norwegian’s serve – one of the most underrated shots on the ATP Tour – holding him steady.
Then came another sharp change, with a series of backhand errors from Ruud allowing Alcaraz to stem the tide with a break of serve at the start of the third.
If the teenager had gotten another chance in the third game, the set would surely have been his. Instead, he let his opponent level when he lobbed a backhand into the net, with some of his play suggesting that the previous five sets had finally caught up with him.
That said dropshots were unusually lacking in their deft touch and his legs were less electric than they often looked.
Rudd had two set points at 6-5 on serve, one of which he saved with a superb stretch volley. The crowd roared their approval at the Quickfire net exchanges, but the tiebreaker was all about the Norwegian’s suddenly poor move.
Knowing the match was there for the taking, he blinked. Twice he hit a backhand from 1-0 down and several errors saw him present it to a tired but determined opponent, who claimed the next seven points.
Rudd said he was happy with his No. 2 ranking but will continue to chase No. 1
The pair show off their silverware after completing the Open final
That put a spring back in the step of the Spaniard, who forced a crucial break at 3-2 when Rudd missed a forehand and then sent a backhand.
Alcaraz becomes the youngest Grand Slam champion since Rafael Nadal in 2005. Ruud is second runner-up for the second time since the French Open, but rises to world number two:
“Things went so well, today was a special night, we knew what we were playing for. It is fitting that the two finalists are number one and two. I’m disappointed not to be number one, but number two isn’t too bad.”
After recognizing the significance of 9/11, like Rudd, an emotional Alcaraz said, “It’s something I’ve dreamed about since I was a kid. I worked really hard on it, there are a lot of emotions at the moment, it’s very special to me.
My mom and grandpa aren’t here, I was thinking about them, a lot of my family couldn’t come here. I’m a bit tired, I always say it’s not a time to be tired, you have to give everything on the pitch, it’s something I work very hard for.’
To see how the match unfolded, read the live blog below from Sportsmail’s Jake Nisse.