The 26-year-old Lyles finished the event in 9.83 seconds to secure victory and record the joint fastest time of this year.
Lyles said he “expected” to win the event despite no one else believing he could.
“It was unexpected for everybody else,” Lyles told the NBC Sports broadcast.
“I believe in myself. I believe in God. I believe in the mission that me and my coach have. We trained nine months for this. For this moment right here.
“You only got one shot to hit your peak and we made sure it counted. Like you said, to do great things, to be one of the legends, you got to win the 100.”
Letsile Tebogo claimed silver finishing in 9.88 seconds, with Zharnel Hughes taking bronze – the Briton just one thousandth of a second behind the Botswana sprinter.
Marcell Jacobs, the Olympic gold medalist in this event, didn’t qualify for the final.
Lyles, who is already a two-time 200m world champion, will go for a three-peat in the event later this week.
At last year’s world championships in Eugene, Oregon, Lyles smashed the American 200m record previously set by Michael Johnson 26 years beforehand and became the third fastest man over the distance after clocking in at 19.31 seconds.