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.
https://www.youtube.com/watch?v=mAw2j0UhQfw
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.
Source: bbc