Michael Phelps became the most decorated athlete in Olympic history when his gold in the 4x200 metres freestyle relay took him to 19.
The 27-year-old had equalled Larisa Latynina's record earlier on Tuesday evening with silver in the 200m butterfly.
The United States swimmer's first gold at London 2012 moved him beyond the Russian whose record had stood since 1964 to stand alone at the pinnacle with three more events to come. The 27-year-old started the evening with 14 gold, one silver and two bronze medals over three Olympic Games since 2004.
He paid tribute to his three relay team-mates after clinching the record. "I told those guys I wanted a big lead in the last leg and they gave it to me, Phelps said. "I just wanted to hold on, I just wanted to thank them for allowing me to have this moment."
Phelps has always maintained he is not interested in medal counts and will be furious with himself after Chad le Clos of South Africa beat him on the touch in the 200m butterfly. It is a measure of the expectations placed on the Baltimore swimmer that there was audible shock around the Aquatics Centre, a feeling of deflation even.
However, credit is due to Le Clos who swam a superb race to take advantage of Phelps' poor judgement, the American gliding into the wall rather than finishing on a full stroke as has been his hallmark. The South African won in one minute 52.96 seconds, 0.05secs ahead of Phelps with Japan's Takeshi Matsuda third.
China's Ye Shiwen won gold in the women's 200m individual medley. The 16-year-old sensation added the title to the gold she won in the longer medley in mind-boggling fashion earlier this week.
Controversy has swirled around the Chinese teenager since her other-worldly victory in the 400 metres individual medley which saw her swim the final length faster than the winner of the men's equivalent, Ryan Lochte. Ye came from slightly down at third at the final turn to produce a storming freestyle leg to secure victory.
When asked after the 200m race if she had used doping to improve her performance, she bluntly replied: "Absolutely not." She added: "I think this is a little bit unfair for me, however I was not affected by that. I'm not affected by the outside noise."
Allison Schmitt of the United States won in Olympic record time in the 200 metres freestyle final. Schmitt, who last month swam the event faster than anyone in textiles in history, led from start to finish and touched in a dominant one minute 53.61 seconds. France's Camille Muffat was second as the pair reversed their placings in the 400m freestyle on Sunday.