Remi Lucidi was last seen knocking on the window of a penthouse on the 68th floor of the 721ft (219m) Tregunter Tower on Thursday, according to the South China Morning Post.
A maid in the building is said to have called police after spotting the 30-year-old outside the window as Mr Lucidi apparently tried to seek help before losing his footing.
Police said the daredevil – who goes by the name Remi Enigma on social media – had fallen before officers arrived.
Mr Lucidi’s sports camera, which contained videos of extreme sports, was reportedly found at the scene, along with his French ID card.
Police said a 30-year-old man’s body was found on a patio in the city’s Mid-Levels area, though they did not release the identity of the person.
“A preliminary investigation suggested the man was an extreme sports enthusiast,” a source told the news site.
“It is possible that he got trapped outside the penthouse while practising an extreme sport in the building, and he knocked on the window for help, but accidentally fell to his death.”
Mr Lucidi reportedly entered the Tregunter Tower, located in Hong Kong’s upscale Mid-Levels district, around 6pm on Thursday and told a security guard he was visiting a friend on the 40th floor.
He was reportedly spotted on CCTV leaving the lift on the 49th floor and again on the staircase to the top floor, where a door had been forced open.
According to the South China Morning Post, he was last spotted by a maid while knocking on a penthouse window at about 7.30pm.
Mr Lucidi last posted on Instagram on 24 July, with a scenic picture from the top of a tower in Hong Kong’s Times Square.
He is said to have checked in to a hostel in Hong Kong on 17 July, according to reports.
Hostel owner Gurjit Kaur told the Post that Lucidi kept to himself, but was a “friendly and humble guy” when they spoke.
“He was healthy and fit and happy faced,” she said on Saturday. “I feel very sad.”
Mr Lucidi previously shared images of himself at the top of tall buildings in Paris, Dubai and Thailand, among other locations.
Fellow urban explorers paid tribute to Mr Lucidi in posts on his Instagram, with one writing: “Rip brother. Sad news no one ever wants to hear about a fellow explorer.”
Another person posted: “Bro went out doing what he loved! He lived his life fully. Not many can say that.”
The Tregunter Towers complex consists of three towers.
The third tower, Tregunter 3, was once the tallest all-residential building in the world, until it was overtaken by Trump World Tower in New York upon its completion in 2001.
