David Rudisha is a double Olympic champion after an emphatic defence of his London 2012 800m title.
The Kenyan superstar, who blitzed the world record in taking gold four years ago, won going away as Algeria's Taoufik Makhloufi taking silver and USA's Clayton Murphy bronze.
Kenyan teammate Alfred Kipketer exploded out the blocks and into the lead in a blistering opening 200m.
But it was too much too soon and he faded as Rudisha took control of the race over the final 300m.
And while Makhloufi and Murphy threatened to challenge on the home straight Rudisha stayed strong to take a second gold medal in a time of 1:42.16, his fastest since that night in London four years ago.
In doing so Rudisha becomes the first man to repeat as 800m Olympic champion since New Zealand's Peter Snell did so in 1960 and 1964.
Rudisha said: "I had no doubts. The feeling in my body was good. It is the greatest moment of my career."