Defending the 100m title for the first time - Dawn Fraser
On December 1st, 1956, Fraser led an Australian medal sweep of the event at the Olympic Games in Melbourne, setting another world record in the process. She gained a second gold medal in leading the Australian team to a world record in the 4x100m freestyle relay and earned a silver medal in the 400m freestyle.
Four years later, at the Olympic Games in Rome in 1960, Fraser repeated her victory at 100m to become the first woman to defend an Olympic swimming title. She also placed fifth in the 400m and picked up silver medals in the medley relay (the first time it was included in the Olympic programme) and in the freestyle relay.