The Dutchwoman is attempting a historic treble of 1500 metres, 5,000 metres, and 10,000 metres.
She started the day by collapsing on the final lap of her 1500m heat, only to get back up and race through the pack to take first place.
She returned to the track later that evening, caffeine-fueled, and was in complete control of a slow-run 5000m, sitting in the pack until unleashing her signature last-lap surge.
Hassan, 28, of Ethiopia, won in 14 minutes 36.79 seconds with a devastating final-lap sprint, but it appears she needed some help crossing the finish line.
“It’s been an incredible day.” “I felt like I was expending so much energy when I fell down and had to bounce up,” she explained.
“I didn’t give a damn before the race here. I was exhausted. I would never be an Olympic champion if it weren’t for coffee.
“I was in desperate need of caffeine!”
Hellen Obiri of Kenya, a two-time world champion, took silver in 14:38.36, while Gudaf Tsegay of Ethiopia took bronze in 14:38.87.
Hassan will compete in the 1500m semi-finals before moving on to the 10,000m final, where she held the world record for two days in June.
On Wednesday, the 1500m semi-finals will be held for the second time.
The athlete has world titles in the 1500 and 10,000 metres, as well as a bronze in the 5000 metres.