Usain Bolt wins Gold for a third consective time to retain 100m gold medal.

9.81s was all it took the world fastest man to retain his olympic gold medal in 100m for the 3rd time.

Justin Gatlin came 2nd with 9.89s while Andre De Grasse of canada came 3rd with 9.91.

Bolt, 29, ran 9.81 seconds to beat Justin Gatlin to gold and follow up his titles at Beijing 2008 and London 2012.

The Jamaican remains on course for the sprint 'treble treble', with the 200m and the 4x100m relay to come.

"I expected to go faster, but I'm happy I won," he said. "I did what I had to."