The Ethiopian-born Dutch athlete came into the marathon on the back of two bronze medals won in the 5,000m and 10,000m in an astonishing bid for podium placings in three events.
And Hassan did not disappoint, holding off Ethiopian Tigst Assefa for victory in an Olympic record of 2hr 22min 55sec.
It mirrored Hassan's efforts in the Covid-hit Tokyo Games three years ago when she also won three medals: two golds (5,000m, 10,000m) and a bronze (1500m).
Assefa took silver in 2:22.58, with Kenya's Hellen Obiri claiming bronze (2:23.10).
"It was not easy," said Hassan. "Every moment in the race I was regretting that I ran the 5,000m and 10,000m. I was telling myself if I hadn't done that, I would feel great today.
"From the beginning to the end, it was so hard. Every step of the way. I was thinking, 'Why did I do that? What is wrong with me?'
"I've never pushed myself through to the finish line as I did today."
Hassan, who won the 2023 London Marathon on her debut at the distance and then produced the second best time ever in winning the Chicago Marathon in October in 2:13.44, said the Olympic gold was a crowning glory.
"I was so happy in the London Marathon, but today I'm more happy, I can't believe I'm Olympic marathon champion!" she said.
"The marathon is something else. When you do 42 kilometres in more than two hours and 20 minutes, every single step you feel it so hard and so painful.
"When I finished, the whole moment was a release. It is unbelievable. I have never experienced anything like that. Even the other marathons I have run were not close to this."
Gruelling climb, perilous descent
The 42km-long marathon course headed out of central Paris on a loop to Versailles, mimicking a key moment from the French Revolution: the Women's March on Versailles, on October 5, 1789, which led to French King Louis XVI finally agreeing to ratify the Declaration of the Rights of Man and of the Citizen.
The route included a 436m climb and 438m descent. The maximum gradient on the route was 13.5 percent.
The 31-year-old Hassan suffered on the gruelling ascent at the 1:38 mark and it looked like that might have been it for her bid for a historic treble.
But Hassan is nothing if not a doughty competitor and she quickly reeled in the lead group on the perilous descent.
Assefa and teammate Amane Beriso Shankule pushed on.
The Kenyan trio of Sharon Lokedi, defending champion Peres Jepchirchir and Obiri stuck with the two Ethiopians as they went through 30km in 1:43.59.
Hassan was toe-to-toe with the east Africans and at the 33km mark, the pack was down to five, Jepchirchir dropped.
Shankule also faded with 2km to run, leaving a gang of four for three podium places.
Like a sprint stage of the Tour de France, the quartet came into the last kilometre sizing each other up, Obiri surging, eyes flicking left and right, all four ready to react at the slightest acceleration.
Hassan probed as the winding finale to Invalides continued, Lokedi failing to match the pace.
And then there were three: Hassan, Assefa and Obiri.
Assefa launched one last attack, dropping Obiri.
It came down to Hassan v Assefa. The Dutch athlete surged around one corner, actually clashing with the Ethiopian.
The pair regained their rhythm and Hassan delivered a perfect sprint finish for a memorable gold.
"At the end I thought, 'This is just a 100m sprint. Come on, Sifan. One more. Just feel it, like someone who sprints 200m'."
