Usain Bolt stormed past his rivals to claim a historic third straight Olympic 100 metres title and declared himself confident of becoming an "immortal" by the end of the Rio Games.
Hot on the heels of a sensational 400m world record by South African Wayde van Niekerk, the Jamaican surged past American rival Justin Gatlin to take the most prized Olympic gold in 9.81sec.
With one title in the bag, Bolt celebrated and turned his attention to completing the 100m, 200m and 4x100m gold medal sweep at three consecutive Olympics.
"This is what we train for. I told you guys I was going to do it," Bolt, 29, told reporters. "Stay tuned, two more to go.
"Somebody said I can become immortal. Two more medals to go and I can sign off. Immortal."
Bolt galloped away in celebration after a superb win, basking in the adulation of the stadium and even taking selfies with fans during his lap of honour.
He then delighted the fans with his traditional "lightning bolt" pose as reggae blasted out of the stadium sound system.
Jamaica's Usain Bolt celebrates after he won the Men's 100m Final during the athletics event at the Rio 2016 Olympic Games at the Olympic Stadium in Rio de Janeiro on August 14, 2016. (AFP)
"It was brilliant. I didn't go so fast but I'm so happy I won. I told you guys I was going to do it," Bolt said.
The victory left Bolt standing alone in the 120-year history of sprinting in the modern Olympic games.
No other athlete - man or woman - has ever won three consecutive individual Olympic sprint titles.
It also leaves Bolt on track to complete an incredible "triple-triple" of clinching 100m, 200m and 4x100m relay titles for a third consecutive Olympics.
Bolt, the 2008 and 2012 Olympic champion, had already earned the right to be regarded as the greatest sprinter in the history of athletics after accumulating more golds on the track than anyone else.
But the Jamaican's latest triumph erases any lingering doubts that he deserves to be ranked alongside the likes of Muhammad Ali, Pele and Michael Jordan as the kind of once-in-a-generation athlete who transcend their sports.
Year of shame
Bolt's win - his 18th gold in Olympic and World Championships since 2008 - averted what might have been a public relations disaster for the drug-tarnished world of track and field.
A corruption scandal involving the sport's former rulers, who were accused of accepting bribes to cover up positive drug tests, and an investigation which alleged an elaborate state-sponsored doping system in Russia have plunged track and field into the worst crisis in its history.
A gold medal for Gatlin on Sunday would have made uncomfortable viewing for many - world athletics chief Sebastian Coe among them - who have advocated that serial doping offenders should be banned for life.
But those fears were swept away by the smiling, laughing figure of Bolt, for so long the sport's most charismatic showman.
Gatlin, who has served two drug bans during his long career, made a powerful start to lead over the first 50 metres.
But as soon as Bolt's head came around the midpoint the American was in trouble and the defending champion surged home around a metre clear of the field.
Jamaica's Usain Bolt (left) crosses the finish line of the Men's 100m Final during the athletics event at the Rio 2016 Olympic Games at the Olympic Stadium in Rio de Janeiro on August 14, 2016. (AFP)
Bolt later said he was dismayed by the reception given to Gatlin.
"I was surprised by it - it was shocking the first time I heard booing in a stadium. However I just focused on my job and got it done," Bolt said.
Gatlin meanwhile put a brave face on his defeat - the eighth out of nine meetings with Bolt.
"At the age of 34, to race these young guys and still make the podium feels so good," said Gatlin, who would have become the oldest Olympic 100m champion in history had he won.
"We work 365 days a year to be here for nine seconds," the 2004 gold medallist added.
Minutes earlier, van Niekerk timed a lightning 43.03sec in the 400m, breaking American Michael Johnson's 17-year-old record.
"I have never seen anything like that," Johnson told the BBC.
"It is amazing. That was a massacre by Van Niekerk. This young man has done something truly special."
Kenya's Jemima Sumgong won the first athletics gold of the day, making light of searing heat to triumph in the women's marathon.
Colombia's world champion Caterine Ibarguen won the women's triple jump with a leap of 15.17m.
Athletics was hit by another doping sensation when the Court of Arbitration for Sport overturned a last-minute ban on Russian long-jumper Darya Klishina imposed by the IAAF world body.
Klishina had been the only Russian competitor accepted by the IAAF for the Olympics after inquiries found mass "state-sponsored" doping in the country.
Media reports said investigators found two bottles of Klishina's urine samples had been tampered with.
The CAS decided, however, that Klishina had met all the conditions set by the world body to take part in Rio. The women's long jump starts on Tuesday.
America's Simone Biles stayed on track for a record five gymnastics gold medals at a single Olympics when she clocked up her third, on the women's vault.
Max Whitlock won the men's floor exercise to become Britain's first Olympic gymnastics champion. He won a second in the pommel horse and was part of another golden day for the British team.
Wimbledon champion Andy Murray won his second straight men's singles tennis gold, beating Argentina's Juan Martin del Potro 7-5, 4-6, 6-2, 7-5 in a marathon final which drained both men.
"Today was a very up and down match, very stressful. Both of us had a lot of chances and it was a long and tiring match. I'm just glad I managed to get through it," said Murray.
Britain's Justin Rose became the first Olympic golf champion in 112 years, edging Sweden's Henrik Stenson on the final hole in a thrilling duel.
"Oh my God. That felt better than anything I've ever won. It was the best tournament I've ever done," Rose said.
A five-gold Sunday for the Brits put them a surprise second on the medals table with 15 victories, behind the United States on 26.
Rio Games security has proved a major headache for organisers, with several teams complaining of thefts and street crime in the recession-hit metropolis.
The latest to fall victim was US swimmer Lochte and three teammates, who said they were robbed at gunpoint by criminals who pulled over their taxi posing as police.
"The guy pulled out his gun, he cocked it, put it to my forehead and he said, 'Get down,' and I put my hands up, I was like, 'Whatever,'" Lochte told NBC News.
"He took our money, he took my wallet - he left my cell phone, he left my credentials."