Phelps gained a measure of revenge against rival Ryan Lochte in their final showdown on Thursday, winning the men's 200-metre individual medley for a record third consecutive Olympics.
Proving once again why he is the greatest swimmer of all time, the American icon becomes the first male swimmer to win the same event at three straight Olympics.
"To be able to win the gold medal and be the first to threepeat, it means something," said Phelps. "It's pretty special and something that I'm very happy for."
Phelps won his 20th career medal, extending the Olympic record he set after earning silver in the men's 200-metre butterfly on Tuesday. He also captured his remarkable 16th gold medal.
Phelps, on world-record time at the various points of the race, finished in a time of one minute 54.27 seconds.
Lochte, the 2011 world champion, earned the silver in 1:54.90, while Hungarian Laszlo Cseh grabbed the final podium spot at 1:56.22.
Lochte, who was upset in the men’s 200-metre backstroke a half-hour earlier, had to still be feeling the effects of that race from both an emotional and physical standpoint.
Knowing his American counterpart was already taxed from the earlier event, Phelps pushed hard from the start, taking the lead after the butterfly — his best stroke.
Phelps kept the advantage over Lochte at the conclusion of the backstroke.
It was smooth sailing from there. Phelps remained strong in the breaststroke before finishing off Lochte in the freestyle.
"I wanted to push the first 100 as much as I could just to kind of see what would happen," Phelps said. "Somebody told me with like 25 to go I was under world-record pace, so it was kind of frustrating I fell a little short."
The London Games have been a disappointment for Lochte. While the 27-year-old has won two gold medals, including the 400-metre IM — destroying Phelps in the process — he's dropped the 200-metre freestyle and 200 backstroke, two races where he came into the Olympics as the world champion.
"I wanted to get all golds in my events, but you know it didn't happen," Lochte said. "I'm going to have to live with that and move on and learn from it. Try not to make the same mistakes in the next four years.
"For the most part," he insisted, "I'm pretty satisfied."
Phelps, also 27, has the chance to win even more medals.
He's set to compete in the 100-metre butterfly final on Friday — where he's the two-time defending Olympic champion — and will take part in the men's 4x100 medley, another event the U.S. team is expected to win gold in.
American Tyler Clary stuns Lochte
First Phelps, now Lochte.
After watching his rival lose in one of his signature events, Lochte experienced the same fate, dropping his Olympic crown in the men's 200-metre backstroke to compatriot Tyler Clary.
Clary charged to a gold medal with a time of one minute 53.41 seconds. Japan’s Ryosuke Irie also bested Lochte, finishing in 1:53.78. Lochte (1:53.94), the 2008 Olympic and 2011 world champion, had to settle for the bronze.
"You always have big dreams in your head that you think you might be able to pull off something like that," Clary said.
"The fact that it just came to fruition is something that hasn't even processed in my mind yet. The fact that I'm now an Olympic champion and Olympic-record holder is something that is very humbling. It's also very motivating for the next four years."
Lochte only had a half hour to get over his stunning loss and prepare for the final showdown with Phelps in the 200 IM, a race he lost.
American Soni breaks a 2nd breaststroke world record
Rebecca Soni of the United States set another world record to defend her 200-metre breaststroke title at the London Olympics.
Soni clocked two minutes, 19.59 seconds to improve on her own mark from Wednesday's semifinals by 0.41 seconds.
It was the sixth world record in the pool at these games.
Satomi Suzuki of Japan touched in 2:20.72 to take the silver medal and Iuliia Efimova of Russia finished in 2:20.92 for bronze.
Soni was also favoured to win the 100-metre breast but took silver behind surprise 15-year-old winner Ruta Meilutyte of Lithuania.
Meilutyte did not enter the 200.
Dutch swimmer wins women's 100m freestyle
Ranomi Kromowidjojo of the Netherlands won the 100m freestyle at the London Olympics.
Kromowidjojo clocked 53.00 to improve on her own Olympic record set in Wednesday's semifinals.
Aliaksandra Herasimenia of Belarus touched in 53.38 to take the silver medal and Tang Yi of China finished in 53.44 for bronze in swimming's signature event.
- Sinead Russell, of Burlington, Ont., finished third in the women 200m backstroke in her semifinal heat and advances to the final.
- Toronto’s Martha McCabe finished fifth in the women’s 200m breaststroke final.
- Mission, B.C., native Brent Hayden, who won a bronze medal in the men’s 100m freestyle, finished seventh in his 50m freestyle semifinal heat and did not qualify for the final.