The man, in his 60s, died in Smallfield, Surrey, on Sunday morning.
His next of kin have been informed. Road closures were in place.
The annual 54-mile bike ride is one of the flagship fundraising events for the British Heart Foundation.
London Mayor Sadiq Khan among 14,000 riders who took part last year.
On its Twitter profile, the charity said: “With a heavy heart we share this news.
“Our team do not have any more information right now but please do keep their family and friends in your thoughts.”
Charmaine Griffiths, chief executive of the British Heart Foundation, which organises the ride, said: “Our deepest sympathies are with the rider’s loved ones.”
Surrey Police said: “We are appealing for any witnesses to this incident to come forward to help our investigation into the circumstances of this incident.”
