Alain Robert began his ascent of the 2,717-tall Burj Khalifa just before sunset and said before he began that he expected his climb to take six or seven hours.
As night fell, a row of powerful spotlights shone on the side of the tower to light the way.
Up in the air: French skyscraper Alain Robert who calls himself 'Spiderman' has begun to scramble his way to the top of the world's tallest tower in Dubai
An ambulance, with a stretcher at the ready, was parked alongside other emergency vehicles at the Burj's base.
Robert has climbed more than 70 skyscrapers, including the Empire State Building, Chicago's Willis Tower and the Petronas Towers in Kuala Lumpur, according to his website.
He conquered Taiwan's Taipei 101, which before the Burj was the world's tallest building, in 2004.
Long way up: Alain Robert began his ascent of the 2,717-tall Burj Khalifa just before sunset and said before he began that he expected his climb to take six or seven hours
Strapped to a safety harness tethered more than 100 stories up, Robert began his climb up the silvery, glass-covered Burj at around 6pm.
He hoisted himself up along a central column, mostly free of decorative rows of pipes that could slow his ascent.
Daredevil: Unlike his many previous climbs, the 48-year-old is using a rope and harness to comply with organizers' requirements in the Gulf sheikdom
Time's getting on: Robert can just be made out near the centre of this picture as he climbs his way up the world's tallest tower in the Gulf Emirate of Dubai, United Arab Emirates
On the up: As night fell, a row of powerful spotlights shone on the side of the tower to light the way
Robert stayed in a Dubai hotel before the climb, doing push-ups, pull-ups and stretches, and loading up on carb-filled foods such as pasta in a room overlooking the target of his latest adventure.
Emaar Properties have not commented on the climb which 'Spiderman' is due to complete this evening.