Record-breaking Michael Phelps became the first swimmer to win four successive Olympic gold medals in one event by beating Ryan Lochte in the 200m individual medley.
Phelps, 31, won his 22nd gold – more than any other Olympian – as fellow American Lochte, 32, faded to a fifth-place finish in Rio.
Phelps finished almost two seconds clear of Japan’s Kosuke Hagino, with China’s Shun Wang taking bronze.
Briton Dan Wallace, 23, came eighth.
Phelps, who posted a time of one minute 54.66 seconds, has won more than twice as many gold medals as anyone else, with former Soviet gymnast Larisa Latynina second on the list with nine.
The American, who retired after London 2012 before returning to the sport in 2014, also has two silver medals and two bronze.
Four of his 22 golds have been won in Rio, where Phelps has added 200m medley success to wins in the 200m butterfly, 4x100m freestyle relay and 4x200m freestyle relay.
He could also win his fourth successive gold in the 100m butterfly after qualifying for Saturday’s final shortly after his 200m medley victory.
Analysis – ‘Phelps destroyed the field’
Adrian Moorhouse, 1988 Olympic 100m breaststroke champion: “What a winner. It’s been a privilege to watch every one of his gold medals, but I don’t think I’ve seen one as emotional as that one. He destroyed the field. It was stunning.”