One man is in a serious condition after hitting a tree near Pyrford in Surrey, whilst the other fell off his bike near Thames Ditton and is being treated for a serious head injury.
Thousands of cyclists have been taking part in the 100-mile race between Central London and Surrey, and many were diverted after the air ambulances were called to deal with the incidents on the route.
The crashes resulted in many cyclists on RideLondon being temporarily halted for approximately half-an-hour.
A spokeswoman for RideLondon said: "The Prudential RideLondon-Surrey Classic was paused.
"This was done on the advice of police on the grounds of public safety due to congestion in Dorking High Street of riders in the Prudential RideLondon-Surrey 100.
"This was caused by a combination of the delay from the earlier stop when a rider required an air ambulance and other riders who were diverted at mile 44".