Bolt strikes again: How the world reacted

Jamaica's Usain Bolt celebrates after winning the gold medal in the men's 100m at the World Athletics Championships. Photo / AP

What the world is saying about Usain Bolt's record ninth World Championship gold medal after he won the 100m title in Beijing, pipping convicted doper Justin Gatlin.

"Usain Bolt will walk away from tonight so proud of himself...this may well have been his finest day. He's saved his title, he's saved his reputation, he may have even saved his sport " BBC pundit and middle distance running great Steve Cram.

"Impossible to be excited for the men's 100m. Three convicted drug cheats ... Three ... Give me a break." A tweet from Alyssia Montano, an American 800-meter runner. (the number is actually four)

"I definitely think this was my hardest race...I've been through a lot this season. It's been rough." Bolt on Bolt.

#BackToBack pic.twitter.com/nHKGo1bEMf

— Usain St. Leo Bolt (@usainbolt) August 23, 2015

"This is a man with nothing else to prove, who's the greatest sprinter of all time. He's been hurt, has every excuse to lose motivation, get distracted, and fade. And yet he summons, on command, breathtaking performances time and time again." Time's Sean Gregory.

"Usain Bolt produced perhaps his greatest performance of all as he put a troubled build-up behind him to beat two-time doper and clear favourite Justin Gatlin to retain his world 100m title." Tom Fordyce, chief BBC sports writer.

"For those who had painted this battle as a nothing less than clash of good against evil in light of the doping issues that have left his sport on life support, Bolt's victory in the Bird's Nest stadium where he made his name may have even secured its future." Owen Gibson, in the Guardian.