South Africa’s Caster Semenya won Olympic gold in the 800m but Great Britain’s Lynsey Sharp missed out on a medal as she finished sixth.
Semenya set a new national record to win in one minute 55.28 seconds and finish well clear of silver medallist Francine Niyonsaba of Burundi.
Kenya’s Margaret Nyairera Wambui took the bronze medal, while Scot Sharp set a new personal best of 1:57:69.
Semenya, 25, has now won two Olympic medals, after a silver at London 2012.
There she finished behind Russia’s Mariya Savinova, who has since been named in a doping report, with the World Anti-Doping Agency saying she should receive a lifetime ban.
Four years on, Semenya finished more than a second clear of Niyonsaba to take the title.
Her time was two seconds adrift of the world record of 1:53:28, set by Jarmila Kratochvilova, running for Czechoslovakia, in July 1983.
“Every athlete’s dream is to win a medal, especially in the Olympics,” said Semenya.