The Dutchwoman had previously taken bronze on 5,000 and 10,000 meters, but had forces left for the demanding marathon course in Paris.
With 150 meters left, Hassan broke away from Tigst Assefa, Ethiopia, and crossed the finish line with a new Olympic record time of 2:22:55.
It wasn't easy. Throughout the entire race, I regretted running the 5,000 and 10,000 meters, says Sifan Hassan.
Two golds in Tokyo
In total, Hassan now has six Olympic Games medals. In Tokyo three years ago, she won two golds and one bronze.
It was so tough from start to finish. Every single step. I've never pushed myself like I did today, says the 31-year-old.
Hellen Obiri, Kenya, took bronze. Swedish Carolina Wikström ran in 2:34:20 and finished 52nd.
"Tough after the hills"
It was something entirely different from other marathons I've run. I've prepared specifically for this course, but it was tough after the hills, says the 30-year-old Uppsala runner to TT.
Halfway through the race, Wikström realized she wouldn't be able to match her 22nd place from her Olympic debut in Tokyo.
I deliberately fell back behind the pack. Then I thought I'd run steadily up the first long hill and then have the strength to push on. But it wasn't easy to push on – it wasn't in my legs.
Even though the result wasn't what Wikström had hoped, she enjoyed the experience.
It was like the Tour de France feeling going up the hills when everyone was screaming. It was packed everywhere. I don't think I'll ever experience anything like that again.