Allyson Felix of the United States won the women's 200 metres gold medal at the third time of asking.
Felix, who had finished runner-up to Veronica Campbell-Brown at the previous two Olympics, came off the bend level with the Jamaican and 100 metres champion Shelly-Ann Fraser-Pryce but lengthened her stride to ease to victory in 21.88 seconds.
Fraser-Pryce of Jamaica took the silver in 22.09.
American Carmelita Jeter won the bronze in 22.14 as Campbell-Brown faded down the home straight to finish fourth.
"It's been a long time coming. I am so overjoyed," said Felix.
"I thought back to the disappointment in Beijing, it's been a long road, I never wanted to give up," the 26-year-old said. "I've wanted it for so long. This moment is really priceless."