(CNN)Shalane Flanagan, a four-time Olympian and the winner of the 2017 New York City Marathon, has announced her retirement after 15 years at age 38.
4-time Olympian Shalane Flanagan retires from professional running
"With happy tears I announce today that I am retiring from professional running," Flanagan wrote in an Instagram post. "From 2004 to 2019 I've given everything that's within me to this sport and wow it's been an incredible ride!"
Flanagan is best known for becoming the first American woman to win the New York City Marathon in 40 years when she won in 2017. She also won bronze in the 2008 Olympics in Beijing in the 10,000 meters, which nine years later was upgraded to silver because the second-place finisher tested positive for doping. Flanagan competed in the Olympics in 2004, 2008, 2012 and 2016.
Her final race was the New York City Marathon in 2018, in which she finished third. She underwent knee surgery in April.
Flanagan was part of a resurgence by American women, including 2018 Boston Marathon champion Des Linden, in the marathon on the world stage.
"I hope I made myself a better person by running," Flanagan wrote. "I hope I made those around me better. I hope I made my competition better. I hope I left the sport better because I was a part of it.
"My personal motto through out my career has been to make decisions that leave me with "no regrets".....but to be honest, I have one.
"I regret I can't do it all over again."