Monger, 25, whose nickname is Billy Whizz after the Beano comic character, is also known for taking part in Celebrity Race Across The World and has covered Formula One and the Paralympics for Channel 4.
An upcoming BBC documentary will show how he beat the world record for a double amputee in the Ironman World Championship in Hawaii.
Monger said: “I’ve spent the last 12 months training 20 hours a week for an Ironman world record attempt, but the thought of donning sequins in front of Craig Revel Horwood fills me with a fear I’ve never experienced before.
“This is about as far from my comfort zone as it can get. My family are big Strictly fans, so I’m doing it for them and to raise awareness for what I’m doing for Comic Relief next year. I’m just hoping my leg doesn’t fall off mid-dance.”
Monger will dance with Strictly professional Nadiya Bychkova, who on this year’s main series was partnered with Olympic swimmer Tom Dean, the first celebrity eliminated in 2024.
How did Billy Monger become a double amputee?
Monger, a Pau Grand Prix in European Formula 3 winner, was injured following a Formula 4 crash in 2017, causing both his legs to be amputated.
He was only the third double leg amputee to complete the Ironman world championship triathlon when he took on the challenge for Comic Relief earlier this year by finishing the 140.6-mile course in Kailua-Kona, Hawaii.
Monger completed it in 14 hours 23 minutes and 56 seconds, more than two hours inside the previous record.
He previously raised £3.2 million for Comic Relief by walking, kayaking and cycling 140 miles across England in 2021.
Strictly Come Dancing’s spin-off show It Takes Two revealed Monger as the sixth contestant for this year’s Christmas special.
Paralympians Jonnie Peacock, who had his right leg amputated below the knee aged five after contracting meningitis, and Jody Cundy, also a lower leg amputee, have both also been on Strictly in recent years.
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You can see how Billy and the other celebrities get on next month.
The Christmas Strictly show line-up will also feature EastEnders star Tamzin Outhwaite, TV presenter and podcaster Vogue Williams, comedian Josh Widdicombe, athlete and Gladiators star Harry Aikines-Aryeetey and Tayce Szura-Radix, who will become the programme’s first drag artist contestant.
The Strictly Come Dancing Christmas special will air on BBC One and BBC iPlayer on Christmas Day.