World 50 and 100m freestyle record-holder Britta Steffen of Germany announced her retirement from competitive swimming on Friday.
The 29-year-old won 50 and 100m freestyle gold medals at the 2008 Beijing Olympic Games, then added the world titles over both distances a year later in Rome, where she set world records in both events on the way to gold.
But Steffen has struggled to maintain that form in recent years, reaching only the 100m semi-finals at the 2012 London Olympics and finishing fourth in the 50m final.
She finished sixth in the 100m freestyle final at the Barcelona world championships in August on her last appearance at a major event.
"I finish my career in the knowledge that I belong to the best in the world," said Steffen, whose partner is Paul Biedermann, the 200m and 400m freestyle world-record holder.
"My health and the support of my family, friends and my partner made it possible for me to keep my body at a high level of performance.
"However, I have doubted in the past few weeks whether I can muster the necessary motivation and energy to fight for gold medals over the next year, or even the next three years."
Christa Thiel, President of the German Swimming Federation (DSV), described Steffen as an "exceptional swimmer, who has made a mark for swimming in Germany in recent years".
