(Reuters) - Marin Cilic broke through for his first Masters 1000 series title on Sunday, beating Andy Murray in the final of the Western & Southern Open and ending the Scot's 22-match winning streak.

The 12th-seeded Cilic, who has struggled to recapture the form he showed in winning the 2014 U.S. Open, produced a dominant serve and booming groundstrokes in a 6-4 7-5 victory.

It was the Croat's first victory in the ATP Tour's premier series in his 71st appearance, and it ended a dominant run by the "big four" of Murray, Novak Djokovic, Roger Federer and Rafa Nadal, who had won the past 18 tournaments in the series.

The loss also put a stop to a grand run by top seed Murray that included his second Wimbledon title and an unprecedented repeat as the Olympic men's singles champion last week at the Rio Games.

"It’s been a great run the last few months, but unfortunately couldn't get it done today," Murray said at the trophy presentation. "We’ll keep working to get better."

Cilic, who lost only three points on serve in the second set, played with passion in winning a slugfest with the Scotsman, who had beaten him 11 of 13 times heading into the final.

"This week was unbelievable for me," said Cilic, who had never gotten as far as the semi-finals in a Masters series event.

"I served extremely well today and that helped me a lot. I felt today that everything was good. I felt that I played really, really high quality tennis."

Cilic took the court some 14 hours after leaving in the wee hours Sunday morning following his three-set semi-final win over Grigor Dimitrov that followed a two-hour rain delay.

Yet the Croat showed no signs of fatigue.

After Murray held his first two service games at love, Cilic scored a break in the fifth game with an overhead smash followed by a forehand winner for a 3-2 lead.

Some Murray miscues led to another break two games later. Although the Briton broke back in the eighth game and held for 4-5, Cilic served up a love game to close out the set.

The second set went on serve until Murray served at 5-5 in a tumultuous game in which Cilic finally broke the world number two on his fifth break point when the top seed dumped a forehand into the net.

Murray got into some snippish exchanges with the chair umpire over his use of the microphone, but in the end it was Cilic who made the biggest noise, rifling a backhand winner to end the match.

Cilic cut loose with a flurry of two-fisted air punches and roared in celebration. After shaking hands with Murray, he leaped high and thrust his arm in victory.

"Big confidence," Cilic said about the upcoming U.S. Open, the year's last grand slam, which starts a week from Monday.

"It's very important for me to continue on this path, to play this sort of game. I may miss some balls, but I have to just push myself and keep going."

(Reporting by Larry Fine in New York; Editing by Andrew Both)