Both birdied No. 16 after play resumed with the sun shining after a delay of 1 hour, 8 minutes for lightning in a round played at times in a driving rain.
Frost didn’t flinch in the showdown with the Presidents Cup captain and World Golf Hall of Famer. Both shot 4-under 68, and Frost finished at 16-under 272.
It was his second victory of the season and fifth career win on the 50-and-over tour. He was making his 17th major start on the tour.
“We both played very hard today. I don’t know who wanted it more, me or him,” Frost said. “He’s just such a tough competitor. I didn’t think I had it in me, all the good shots he hit out there. I just had to try to stay on top of him.”
Couples was seeking a second consecutive win in a major.
LPGA TOUR: In Pittsford, N.Y., Inbee Park birdied the third hole of a sudden-death playoff with Catriona Matthew to win the rain-delayed LPGA Championship on Sunday.
Park made a 20-foot putt on the par-4 18th to go 2-for-2 in LPGA Tour majors this season. She rebounded in the playoff after relinquishing a three-shot lead with a final-round 3-over 75. Park bogeyed three of her final five holes in regulation.
Matthew shot a bogey-free 68 to match Park at 5-under 283 at Locust Hill.
After both made par on the first two playoff holes, Matthew struggled off the 18th tee. After having difficulty advancing the ball out of the rough just below the green on her third shot, Matthew missed a 50-foot par chip.
Park also won the Kraft Nabisco in California in early April and has four victories this year. With the victory, Asian players have won nine straight majors.
EUROPEAN TOUR: In Atzenbrugg, Austria, Joost Luiten won the Lyoness Open by two shots for his second European Tour title.
After holding a three-stroke lead overnight, Luiten shot 71 in the final round Sunday to finish at 17-under-par 271 on the Diamond Country Club course.
Thomas Bjorn (68) finished second at 15 under.