The 31-year-old is seeking to become the first woman to win gold in the three events, emulating the great Czech athlete Emil Zapotek, who achieved the men's triple in Helsinki in 1952.
"I am excited to announce I will run the 5000m, 10,000m, and the marathon here in Paris," Hassan said on social media.
"I am a curious person looking forward to the challenges, and trying to find out what is possible. I love the journey as much as the challenge," she added.
Hassan is no stranger to making history. At the Tokyo Games, she became the first athlete ever to win medals (two gold, one bronze) in the 1,500m, 5,000m, and 10,000m.
Dropping the 1,500m to run the marathon is a step into the unknown, she acknowledged, although she is not a novice at the latter having made a stunning debut in winning last year's London Marathon.
"Did I balance speed on the track with enough endurance in the marathon? Let's find out together," she said.
"It's not easy to face the unknown but my curiosity has driven all my training towards this goal. I will try my best to succeed."
The schedule will certainly test her powers of recovery.
The 10,000m final is scheduled for 1900GMT on Friday 9 August, only 35 hours before the marathon starts at 0600GMT on Sunday 11 August.
Before that, she will run 5,000m heats on August 2 with a likely final on August 5 -- a total of 62.195 kilometres of Olympic competition.
"It has been a huge challenge to prepare myself because the way of running, the energy required... everything is different between track and the marathon," she said.
Hassan arrived in the Netherlands as a 15-year-old refugee from Ethiopia but has never explained why she left her native country.
In Tokyo, she recovered from a dramatic fall in the 1,500m to snatch bronze, before bouncing back from that disappointment to secure gold in the 5,000m and 10,000m.
Her Paris ambitions impressed US track legend Michael Johnson, who wrote on his account on Twitter, formerly X: "For anyone else this would be insane!"
"I don't believe there's ever been an athlete who enjoys racing more than Sifan Hassan," he said.
