The BBC Radio 2 presenter began his 4 Nations Cycle Challenge from BBC Scotland’s home at Pacific Quay in Glasgow just after 8am this morning.
He was cheered on by comedian Susan Calman, DJ Spoony and drummers from Glasgow’s Samba Ya Bamba band.
He will cover nearly 400 miles over five days, cycling through Scotland, Northern Ireland, England, and his native Wales.
Owain said: “I am very nervous for what the next couple of days have in store for me.”
On Monday’s BBC Radio 2 Breakfast Show, he told Sara Cox: “Glasgow is gorgeous this morning.
“Honestly, we couldn’t have hoped for better weather to kick off the challenge.”
He set off on a bike named Shania Chain, painted in Pudsey Bear’s signature yellow with coloured spots.
His first day’s route, will see him ride 84 miles from Glasgow to Cairnryan, where he will catch a ferry to Northern Ireland.
A bagpiper played Scotland the Brave as he set off.
The challenge will take him through all four UK nations, finishing in central Cardiff on Friday, November 13.
The route includes three major climbs and covers the greatest distance ever attempted in a Radio 2 fundraising challenge.
DJ Spoony said: “I’ve given him about five big hugs, he doesn’t need it, he seems in the finest fettle in a glorious Glasgow morning.
“I feel safe that he’s going to do this challenge with aplomb.
“He looks incredible.
“He’s in great spirits and away we go.”
Singer Shania Twain also sent a message of support after learning the bike was named in her honour.
The public can follow his route in real time through a live tracker on the BBC Children in Need website.
