Swimming at the 2012 London Summer Games:

The 2008 Olympic version of this race had been one of the closest races in Olympic history with Michael Phelps out-touching Serbian Milorad Čavić by only 1/100th of a second. Both were back in London and both made the final. Phelps' best stroke was the butterfly and he had won the 100 and 200 butterfly at the 2011 World Championships, as he had done at the 2004 and 2008 World Championships. But he had earlier faltered in the 200 fly in London, winning "only" silver behind South African Chad le Clos.

The final saw the early lead taken by Čavić and German Steffen Deibler, with Phelps seventh at 50 metres, leading only Le Clos. But the final lap was all Phelps as he finished in 51.21 to three-peat in the event, with Le Clos also coming on strong to finish in a second-place tie with Russian Yevgeny Korotyshkin. Fourth-place was also a dead-heat between Deibler and Čavić.

For Phelps this was his final individual gold medal of a vaunted Olympic career. It was his 11th individual gold medal and 17th gold medal in all – he would later win #18 in the 4×100 medley relay. His three-peat in this event followed a similar three-peat he had just completed in the 200 IM, making him the first man to three-peat in a swimming event at the Olympics, and only the third person ever, following Australian Dawn Fraser in the 100 freestyle in 1956-64, and Hungarian Krisztina Egerszegi in the 100 backstroke in 1988-96.