
The 35-year-old golden girl of US athletics, who is bidding to become the most decorated female Olympic track and field athlete in history, clocked a season best 49.89s to finish second in her semifinal.
Jamaica’s Stephenie Ann McPherson took first place with a personal best time of 49.34s, the fastest time of the semifinals.
Felix, who is competing in her fifth and final Summer Games, is tied with Jamaican legend Merlene Ottey as the most decorated female track athlete in Olympic history on nine medals.
Reigning Olympic champion Shaunae Miller-Uibo of the Bahamas also advanced safely, winning her semifinal in 49.60s.
Marileidy Paulino of the Dominican Republic won the remaining semifinal in 49.38s, with Candice McLeod second in 49.51s.