The 22-year-old American - who has earned comparisons with retired Jamaican legend Bolt - went clear at 50 metres out to cross the line in 19.83 seconds and went and hugged his mother.
"This time last year I'd only just started running," said Lyles.
"Think of that.
"Don't say I'm the new Bolt. I'm me. If you like me, I'll happily entertain you. It's my time."
Canada's Andre De Grasse took silver in 19.95 and Alex Quinonez of Ecuador finished third in 19.98.
Lyles -- who has run quicker over 100m and 200m than Bolt at the same age -- was behind Britain's Adam Gemili entering the straight but powered past him.
In winning, Lyles also delivered the perfect response to Bolt questioning prior to the championships if he could handle the pressure.
"So many times this year I've thought of being world champion, you wouldn't believe it," he said.
"I have it on my phone, I say it to myself in my car, I think it all the time -- and finally to have done it feels unbelievable."
Lyles, who dyed his hair silvery-grey, said he had the self-belief he could dig deep enough if he was in a hole to come through and win.
"I don't know how many people come to their first World Championships and get the gold, but I've done it," he said.
"I just knew no matter what position I found myself in I can always find a way to come through.
"And when I crossed the line I just felt relief."
De Grasse, bronze medallist in the 100m, added yet another medal to his growing collection as both he and surprise package Quinonez, the PanAm champion, passed a tiring Gemili.
"I think it was part of my comeback I was a little bit tired coming into the final," said De Grasse, who has been beset by hamstring problems in the past two years.
"I had setbacks even on my comeback and was not always able to train every day as I was nervous I would be injured aagin.
"Next year I will be stronger definitely and this is a step in the right direction."
It was more agony for Gemili as he had been edged out of the bronze in the 2016 Olympic final.
2017 champion Ramil Guliyev of Turkey - who had strapping on his right knee - finished fifth.