Olympic swimmer Missy Franklin retires at 23

In this Aug. 3, 2012, file photo, United States' Missy Franklin holds her gold medal in the women's 200-meter backstroke final at the Aquatics Centre in the Olympic Park during the 2012 Summer Olympics in London. (AP Photo/Michael Sohn, File)

In this Aug. 3, 2012, file photo, United States' Missy Franklin starts in the women's 200-meter backstroke final at the Aquatics Centre in the Olympic Park during the 2012 Summer Olympics in London. (AP Photo/Michael Sohn, File)

In this Aug. 3, 2012, file photo, United States' Missy Franklin reacts to her gold medal win in the women's 200-meter backstroke final at the Aquatics Centre in the Olympic Park during the 2012 Summer Olympics in London. (AP Photo/Michael Sohn, File)

Five-time Olympic champion Missy Franklin is retiring from swimming at age 23. She cites chronic shoulder pain that has affected her for the last 2½ years.

She announced her plans Wednesday in a letter posted on ESPN.com.

Franklin’s success and bubbly personality made her a darling of the 2012 London Olympics. At age 17, she became the first woman to win four gold medals in a single Olympics in any sport.

This was perhaps the hardest letter I’ve ever had to write. There are so many words to say and I thank you all for letting me share them with you, and for your continued support. Today, I announce my retirement from competitive swimming. https://t.co/P3wLMnOWck

— Missy Franklin (@missyfranklin) December 19, 2018

At the 2016 Rio de Janeiro Games, Franklin failed to make the finals in either of her two individual events and won her only medal, a gold, by swimming the preliminary heat of the 4×200-meter freestyle relay.

She had surgery on both shoulders early last year, but the pain never completely subsided.

Franklin’s last competitive race was in the 200 free at the U.S. nationals in July. She finished third in the C final.