BEDMINSTER, N.J. — Sung Hyun Park, a 23-year-old South Korean with a fluid swing and stalwart nerves, dropped a 20-foot putt on the 15th green and then a 6-footer on the 17th, capturing the United States Women’s Open with the decisive birdies on Sunday.

Consistency and length carried the day for Park, who carded only one bogey to shoot a five-under-par round of 67 at Trump National Golf Club. Park chased and then surpassed Hye-Jin Choi, a plucky 17-year-old amateur from South Korea, playing one pairing behind her. Choi dumped a critical seven-iron shot off the tee into a pond on the 16th to wreck her own fairy tale.

Feng Shanshan of China, the front-runner for most of the tournament, imploded on the final hole with a triple-bogey 8, dropping her into a tie for fifth at six under.

“I have had a lot of winnings, but winning here at the U.S. Open means so much more,” said Park, who had seven victories on the Korean tour last year.