She first learned to swim in her backyard pool in Katherine, Northern Territories. As a ten-year old Brisbane school girl, she watched Samantha Riley win the bronze medal in the 100m breaststroke at the 1996 Olympic Games in Atlanta. Less than four years later, she ousted her idol from the Australian Team by winning the 100m breaststroke at the 2000 Australian Olympic trials at the age of 14. Shortly after her fifteenth birthday, she swam the race of her life to claim the silver medal in the 100m breaststroke and added another silver in the 4x100m medley relay at the Sydney Olympic Games.
At the Athens Games in 2004, she won a bronze medal in the 100m breaststroke, a silver medal in the 200m breaststroke and gold in the 4x100m medley relay. After that she was the most dominating female breaststroker in the world, setting six world records, three in the 100m and three in the 200m. She was named World Swimmer of the Year in 2005 & 2006, and in 2007 she dominated her specialty at the FINA World Championships again. The pinnacle of her career came with her first individual Olympic gold medal in the 100m breaststroke at the 2008 Beijing Olympic Games, where she also won a silver medal in the 200m breaststroke and a second gold medal in the 4x100m medley relay.
After a brief break in 2009, she returned to the pool and four years later, when she qualified for the London Olympic Games in 2012, she became the first Australian swimmer to compete in four Olympic Games. Along with Ian Thorpe, she holds the record for the most Olympic medals (nine) won by any Australian, in addition to winning seven FINA World Championships.
Nicknamed “Diesel”and “Lethal Leisel,” she became one of the most popular and visible sports figures in Australia. As she candidly recounts in her 2015 autobiography, Body Lengths, that her achievements and celebrity were not without their challenges. In her book she tells what it was like to be thrust into the limelight so young and under constant pressure from an early age to be perfect — from coaches, from the media and from herself. Despite the highs of her swimming stardom, she suffered depression, and at one time planned to take her own life. In Athens she was criticized for failing to win the gold in the 100m breaststroke. In London, in 2012, she was criticized in the media for her weight, but she handled herself with great composure. She has emerged with maturity and good humor, having finally learned how to be herself and live with confidence. She also hopes that by telling her story, other female athletes will understand they are not alone.