Shaunae Miller (BAH) of Bahamas reacts after winning the gold medal in the women's 400m final during the 2016 Rio Olympics in Brazil, Aug 15, 2016. [Photo/Agencies]

Miller retained the lead coming off the final bend but started tightening up as Felix surged about 50 metres from the line and the pair were neck-and-neck until the Bahamian's gold medal-winning dive.

Jamaica's Shericka Jackson took bronze in 49.85 ahead of Americans Natasha Hastings (50.34) and Phyllis Francis (50.41) in fourth and fifth.