Missy Franklin, a five-time Olympic champion, announced her retirement from swimming at the age of 23, citing chronic health problems.
In a retirement letter published on ESPN, a U.S.-based sports television channel, on Wednesday, Franklin said it was hard for her to take this decision.
"It took me a long time to say the words 'I am retiring'. A long, long time. But now I'm ready," she wrote.
On her history of injuries while preparing for the Olympics in 2016, Franklin said she "endured shoulder pain whenever I tried to train or compete, depression, anxiety and insomnia".
"But now, I'm ready. I'm ready to not be in pain every day. I'm ready to become a wife and, one day, a mother," she added.
The American swimmer won 4 gold medals at 2012 London Olympics when she was 17-year-old.
