Bolt had stumbled out of the blocks in winning his semi-final but managed to run a season's best time of 9.79 seconds to win in the final.
Justin Gatlin had been unbeaten in 28 races and started off as favourite after running a fast time in his semi-final.
But there was no beating Usain.
The Jamaican took the title for the third time.
Sprinter Usain Bolt has beaten Justin Gatlin to win the 100m title at the World Athletics Championships.