American Phyllis Francis ripped up the form book to claim a shock gold in the women's 400m at the IAAF World Championships on Wednesday.
The race had been billed as a straight duel between multi-medalled American Allyson Felix, the defending champion, and Olympic champion Shaunae Miller-Uibo.
But clear leader Miller-Uibo tied up in shocking fashion with 20 metres to run to allow hard-charging Francis, 25, win with a personal best of 49.92 seconds.
Bahrain teenager Salwa Eid Naser claimed silver in a national record of 50.06, with Felix taking bronze, just 0.02sec adrift, as Miller-Uibo went from first to fourth in the final strides.
Francis, who finished fifth at the Rio Olympics, was left stunned by her victory.
"It is amazing. I am so excited. It is such an amazing feeling. Being world champion sounds pretty cool. This win has not hit me yet, but I guess tomorrow when I will wake up," the 25-year-old said.
"Allyson and Shaunae are amazing finishers, we are that talented. When I went down the home straight I just believed in myself and stayed patient.
"I just knew what I was capable of doing, so I stuck to my race model.
"At the finish line I was surprised, I thought I was second or third, but then they told me 'you are first'. That is crazy."
Naser, 19 and born to a Bahraini father and Nigerian mother, said she had "surprised my opponents and I even surprised myself".
"Coming to these championships, I really did not think about a medal.
"I was not chasing Felix, I was pushing myself until the very end and I did not even see what was going on in the last metres."