Jamaica's Usain Bolt became the first athlete to win three Olympic 100m titles by beating American Justin Gatlin to gold .
29-year-old Bolt, ran 9.81 seconds in his final Olympics to replicate his success at Beijing 2008 and London 2012.
Gatlin, twice banned for doping offences, finished 0.08 seconds behind Bolt to take silver.
Canada's Andre de Grasse took bronze in a personal best of 9.91, ahead of Bolt's Jamaican team-mate Yohan Blake.
Bolt remains on target to leave Rio with a third successive Olympic treble after winning the 100m, 200m and 4x100m relay titles in 2008 and 2012.
The world record holder said in February he would retire from athletics after the 2017 World Championships.