Hellen Obiri, a two-time Olympic silver medalist in the 5,000 meters, won the women's Boston Marathon in a sprint down Boylston Street to finish in 2:21:38.
Running her second marathon, Obiri hung in with a tightly packed lead group for the entire race before breaking away with a mile to go and won to roars of approval from the fans.
"I tried to be patient and wait for the right time to happen," said Obiri, who finished sixth last fall in New York in her marathon debut. "Today was my time."
Ethiopian Amane Beriso, a favorite after producing the all-time third-fastest marathon in Valencia late last year, was unable to find her kick and could only watch helplessly as Obiri zoomed past. She finished 12 seconds behind.
Israeli Lonah Salpeter, who claimed bronze at the World Championships last year, survived a duel for third in 2:21:57, keeping Ethiopian Ababel Yeshaneh off the podium.
Obiri said in a televised interview that she very nearly opted out of the race after moving to the United States just three weeks ago and drew on the lessons from her marathon debut in New York last year, where she finished sixth.
"I was feeling like my body was ready," she said. "I believed in myself."
Obiri's victory completed the third straight Kenyan sweep after defending champion Evans Chebet won Monday's men's race.
Information from Reuters and The Associated Press was used in this report.