The 25-year-old Beijing gold medallist confirmed the news via a video posted on her website on Wednesday.

Injury-plagued Rice has not raced competitively since her unsuccessful 2012 London Games campaign, having undergone three shoulder operations.

"London was really tough," she said.

"There were so many things that went wrong for me in that preparation and it was like I was trying so hard to make everything so perfect and everything went wrong.

"Coming off the Games, I really didn't want to make a rash decision on my career and if I was going to keep swimming or not because I was still too emotional about the whole preparation that I'd just been through.

"I felt a lot of pressure to live up to everyone's expectations and fulfil their answers, but I knew I had to take the time for myself to get to the point where I knew 100 per cent what I wanted to do."

Rice said she never wanted to make a comeback and was final about her "sad" decision.

"I definitely feel like I'm losing a part of myself but I'm really excited about what's to come," she added.

Rice did not say what she will do next, but declared her intent to "prove myself out of the water".

The Queenslander collected three gold medals and three world records in the 200m and 400m individual medleys and the 4x200m freestyle at the 2008 Olympics.

She is one of just seven Australians to win a treble at a single Games.

AAP