Murray finished a stunning, rain-interrupted 6-2, 7-6 (5), 4-6, 6-4 victory Sunday at Flushing Meadows to reach his first Grand Slam final and stop the No. 1-ranked Nadal's 19-match winning streak at major tournaments.
Trying to become the first British man to win a major tennis championship since Fred Perry at the 1936 U.S. Open, Murray will face four-time defending champion Roger Federer in the final Monday night.
"He's got loads of experience in these situations," Murray said, "and it's something new to me."
The sixth-seeded Murray won the first two sets against Nadal and was down a break at 3-2 in the third when play was suspended Saturday because of Tropical Storm Hanna.
"Tough to sleep," Murray said.
As should surprise no one, the generally indefatigable Nadal made a stand Sunday, taking the third set and going ahead 3-1 in the fourth. But Murray took five of the last six games, breaking Nadal twice and ending the Spaniard's bid to make his first final at the U.S. Open.
Murray never before made it past the quarterfinals at a major and never had defeated Nadal in five previous tries. Nadal, meanwhile, won 54 of his preceding 56 matches and took the titles at the French Open, Wimbledon and Beijing Olympics.
But Murray, the 2004 U.S. Open junior champion, was up to the task this time. He wound up with more than twice as many winners as Nadal, 65-32.
Murray won a 22-stroke point with a volley winner to get to match point, leaving Nadal bending over behind the baseline, chest heaving. Then Murray completed the service break to end the match, easily chasing down Nadal's drop shot and smacking a winner.
"I just had to keep my head down and watch the ball - and that was that," Murray said. "I didn't feel particularly nervous."
Murray immediately turned to his private box, closed his eyes and leaned backward. With the crowd cheering, he threw his two wristbands and white baseball cap into the stands.
During an on-court interview afterward, Murray described himself as "very relieved" to have won and to have reached the title match at his "favorite tournament" - which might draw some winces in the land of Wimbledon.
He explained, though, that he was thrilled to have seen his favorite comedic actor, Will Ferrell, in the stands Sunday, and was also excited to have spotted members of the cast of the TV show "Entourage" at the tournament.
"That's awesome," the 21-year-old Murray said. "You don't get that back home."
Others might be star-struck staring across the net at Federer, who will be attempting to win his 13th Grand Slam title while Murray chases his first.
But get this: Murray owns a 2-1 career mark against Federer.
"He's probably the greatest player ever, so to get the chance to play against him in a Slam final is an honor," Murray said. "But I've played well against him in the past and hopefully... I'll do that again tomorrow."
Serena Williams was to face Jelena Jankovic on Sunday night in the women's final, postponed a day because of rain. Williams was seeking her third U.S. Open title and ninth major title overall.
Nadal, meanwhile, was hoping to become only the fourth man in the 40-year Open era to win three consecutive Grand Slam titles, joining Rod Laver, Pete Sampras and Federer. But Nadal has never had as much success on the hard courts of the U.S. Open as on the clay of Roland Garros or the grass of the All England Club.
He beat Federer in the finals at both of those places this year and surpassed him atop the rankings last month.
On Saturday and Sunday, though, Murray exhibited precisely the sort of winner-evaporating defense that Nadal usually employs to wear down opponents.
Murray also stood waaaaaaay back to return serves, sometimes 10 feet behind the baseline, in order to better adjust to the heavy spins Nadal uses.
It was the mix of strokes and smarts that have allowed Murray to progress so quickly and guarantee that he'll reach a career-high ranking of No. 4 after the U.S. Open. One sign of his growth: He had won only two of 14 sets he and Nadal had played as professionals, then matched that total Saturday.
Murray faced some real tests of nerves in the fourth set, including a break point in the first game that he saved with one of his 21 aces.
Another gut-check moment came in the next game, when Murray accumulated seven break points - and let all go to waste, part of a span in which he went 0-for-15 on such chances. It was a 22-point, 15-minute novella of a game, filled with highs and lows, physical and mental, for both men.
Murray might have folded there and, indeed, his downward spiral continued when he made four unforced errors and was broken at love to fall behind 2-1.
"The momentum was kind of with him a little bit," Murray said. "I just had to stay aggressive, stay focused."
He did just that.
Trailing 3-1, Murray fell behind love-30 in his next service game. But the Scotsman took advantage as Nadal sailed two forehands long around a missed drop volley try, and Murray broke to get even at 3-3.
The crowd was supporting Nadal, something Murray understood completely.
"If I was a spectator," Murray said, "I would have rather watched more tennis as well."
Now he'll have as good a view as possible of Federer.
"I played well enough to beat the No. 1 player in the world over two days, and I've beaten Roger in the past," Murray said. "I have the tennis to compete with those guys."