Olympic swimming legend Dawn Fraser has revealed the worst day of her life, saying that she was behind the wheel when her mother was killed in a car accident.

The 83-year-old four-time Olympic gold medallist told The Courier Mail about the secret she'd kept inside for decades.

"I burst out that I was driving the car that killed my mother," Fraser explained, saying that the incident happened at a training camp in South Australia in 2019.

"Everyone burst into tears and I cried with them.

"It got me over some sort of hurdle. I'd just locked it up inside of me."

The accident happened in 1964 when Fraser was 26. In the accident, Fraser suffered from fractured vertebrae and torn ligaments in her knees, but her mother was pronounced dead at the hospital.

She also opened up about surviving two separate sexual assault incidents in her 20s.

"That was one of the most horrific times of my life," she said.

"So horrific I put it in the back of my mind and try not to think about it… It's in the past and I don't live in the past."

Fraser is often regarded as Australia's greatest Olympic athletes as she's won four gold medals and four silver medals in the games. She's also won seven gold medals and a silver at the Commonwealth Games.