Christian Coleman shrugged off the controversy of his build-up to the World Championships to win the 100m final in 9.76 seconds.
The pre-event favourite, who avoided a ban for three missed doping tests, finished well clear of defending champion and fellow American Justin Gatlin, who clocked 9.89 in Doha.
Canada’s Andre de Grasse took bronze in 9.90.
Britain’s European champion Zharnel Hughes was sixth in 10.03.
Although Coleman will receive generous plaudits for his display here, USA track great Michael Johnson said prior to the competition that controversy surrounding Coleman “completely disqualifies” him from being the face of the sport.
The US Anti-Doping Agency charged Coleman with missing three drugs tests in 12 months before withdrawing the claim.
“I am humble, I am just here to win titles,” an elated Coleman said afterwards.
“It is an incredible time. I think the sky’s the limit, I think I still have a lot of things I can work on and improve, I think I can keep dropping my time.”
For the second successive day the crowd was sparse inside the Khalifa Stadium, which can hold 40,000. There has been no update as to whether the organisers have improved on sales of 50,000 tickets for the entire 10 days.
On Saturday, the stadium became more vacant as the evening wore on and only a few witnessed the spectacular light display before the men’s 100m final.
Much of the focus leading up to the championships was about whether Coleman or his USA team-mate Noah Lyles – competing in the 200m – would take the title of ‘sprint king’ following Usain Bolt’s retirement after London 2017.
That projected battle was thrown into serious doubt when it was announced in August that Coleman was under investigation for missing three tests in 12 months. If found guilty, the 23-year-old from Atlanta faced a one-year ban.
However, the US Anti-Doping Agency, which initially charged Coleman, withdrew the case after it was proved there had been a filing irregularity regarding the date of the first missed test.
Seemingly unaffected by the drama, Coleman cruised through the rounds before once again making his superiority count in the final.
Defending champion Gatlin, who is also a controversial figure having twice served doping bans, produced another excellent display in a final.
Having won the Olympic title back in 2004 and now aged 37, he still remains a force in men’s sprinting and must be regarded as an Olympic medal contender for Tokyo 2020.
Hughes might feel disappointed with his display. The Anguilla-born sprinter, fifth at the 2015 championships, looked comfortable in his heat and semi-final but failed to recreate that level of performance when it mattered most.
“My body wasn’t feeling up for it tonight unfortunately,” said Hughes, who will go on to compete in the 200m.
“When I pushed out I was all over the place and I lost my form and I’m not happy with that, but I live to fight another day.”
Great Britain’s Adam Gemili and Ojie Edoburun failed to progress beyond the semi-finals.
Gemili, who will also run the 200m, was just edged out into third in his semi while Edoburun came fifth.
Earlier in the day Dina Asher-Smith, one of Britain’s main medal hopes, eased into Sunday’s 100m semi-finals but it was the performance of Jamaica’s Shelly-Ann Fraser-Pryce that drew gasps from the crowd inside the Khalifa Stadium.
The 32-year-old, 10 years after completing her first Olympic and world double, looked relaxed as she powered past her rivals to cross the line in a time of 10.80 seconds – the fastest ever at this stage of the event at a World Championships.
As for Asher-Smith, she also dipped under 11 seconds – for the seventh time this year – and won her heat comfortably. The only other sprinter that managed a sub-11 seconds run was Ivory Coast’s Marie-Josee Ta Lou, who won her race in 10.85.
Britons Daryll Neita and Imani Lansiquot also progressed, as did Rio 2016 gold medallist Elaine Thompson and the USA’s defending champion Tori Bowie.
‘We will see what happens’ – Giles
The British trio of Elliott Giles, Kyle Langford and Jamie Webb all qualified for Sunday’s 800m semi-finals.
Giles, 25 – the 2016 European bronze medallist – led almost from start to finish to clock the fourth fastest time of the heats – one minute 45.53 seconds.
He told BBC Sport: “It was more mindset. KISS – keep it simple. I knew what I needed to do. I don’t need to over-complicate it, just run. Richard Kilty said, ‘over analysis leads to performance paralysis’. That has stuck with me. All we have to do is run and we will see what happens.”
European indoor silver medallist Jamie Webb finished third in his race while Kyle Langford, a surprise fourth two years ago, went through as a fastest loser.
Britons Shelayna Oskan-Clarke and Alexandra Bell both failed to qualify for Monday’s 800m final. Oskan-Clarke, the world indoor bronze medallist, was in a good position in the final 60 metres but tripped as she approached the line.
Brilliant Hassan takes 10,000m title
There were three other medals won inside the stadium. Jamaica’s Tajay Gayle surprised his more illustrious rivals by winning the long jump with 8.69m.
Olympic champion Jeff Henderson clinched silver with 8.39m and Cuba’s world indoor champion Juan Miguel Echevarria took bronze with 8.34m.
Remarkable Dutch athlete Sifan Hassan who has previously won world medals in the 1500m and 5,000m added 10,000m gold with a world lead time of 30 minutes 17.62 seconds. And the USA’s DeAnna Price won the hammer title with a distance of 77.54m.
Elsewhere, Norway’s world champion Karsten Warholm and his main rival Rai Benjamin, of the USA, both eased into Monday’s 400m hurdles final.
Both the men’s and women’s 50km walk races take place later, a day after the competitors in the women’s marathon struggled with the heat and humidity at Doha’s Corniche.