Allyson Felix produced the fastest time in the world this year of 21.82 seconds as she defended her World Championship 200m title in Osaka on Friday night.

The 21-year-old American star shrugged off the nervousness she showed before the start to win the eagerly-awaited final ahead of Jamaica's Veronica Campbell and Susanthika Jayasinghe of Sri Lanka.

Felix produced a lifetime best, her first-ever sub-22sec clocking, as she pulverised the opposition coming into the home straight.

Campbell, who was chasing a double after winning the 100m, held a stride advantage at that point, but had no answer to Felix's renowned finishing speed.

The Olympic silver medallist, with tremendous acceleration 70 metres from the line, quickly opened a huge gap to decisively beat her Jamaican rival by 0.53sec.

Behind Campbell, who beat Felix for Olympic gold in Athens three years ago, Jayasinghe clocked 22.63sec.

"I feel so good, I am so excited," was the reaction of Felix afterwards.

"Tonight is special. I have been waiting for so long to run such a time, to run under 22 seconds and it has not been an easy road but finally I managed.

"Running so fast feels great. But it was not really that easy. Everything went as I wanted."