TOKYO — Jasmine Camacho-Quinn of Puerto Rico won the women’s 100-meter hurdles on Monday morning, beating Kendra Harrison of the United States, the world-record holder.

Camacho-Quinn, a University of Kentucky graduate, was the favorite coming in on the strength of a perfect season and an Olympic record of 12.26 seconds in the semifinal. But Harrison had the experience and had gotten the best of her in their meetings over the years.

Camacho-Quinn broke fast, then powered away after halfway to win comfortably in 12.37 seconds. Harrison was second in 12.52, three-hundredths of a second ahead of Megan Tapper of Jamaica.

It was only the second Olympic gold medal for Puerto Rico, following Monica Puig’s win in women’s tennis at the 2016 Games. It was Puerto Rico’s first gold in track and its second medal in the sport, after a bronze in the men’s 400 hurdles for Javier Culson in 2012.

“I am pretty sure everybody is excited” in Puerto Rico, Camacho-Quinn said. “For such a small country, it gives little people hope. I am just glad I am the person to do that.”

Camacho-Quinn had hit a hurdle and failed to qualify from the semifinals of this event in 2016. Her brother, Robert Quinn, is a linebacker for the Chicago Bears.

Harrison had been a medal favorite in 2016 but failed to qualify at the Olympic trials that July, before setting the world record at 12.20 later that month. “I missed out in 2016, so to come here and get a medal for my country, I couldn’t be happier,” she said Monday.