The man was rescued by Bowland Pennine Mountain Rescue Team after he fell into a deep ditch next to the forest's mountain bike trails at 1.30pm.
In the team's 61st call out of the year, a total of 12 volunteers were mobilised and rushed to his aid, where they discovered that his injured ankle was facing the wrong way.
The air ambulance was called into action whilst the mountain rescue teams made their way through the depths of the forest to locate the injured cyclist.
The man was given gas and oxygen to help relieve some of his pain whilst the team secured his ankle with a splint, before he was handed into the care of the ambulance service and rushed to Airedale Hospital in West Yorkshire.
A spokesman for BPMRT said: "We received a call from the North West Ambulance Service about a male mountain biker who had fallen on the trails at Gisburn Forest.
"When we arrived on scene we quickly attended the mountain biker who had quite clearly damaged his ankle (it was facing the wrong way!).
"The North West Air Ambulance arrived and together we treated the casualty and after splinting his ankle he was evacuated to a land ambulance and transported to Airedale Hospital.
"A very big thank you to our Team members and to the North West Air Ambulance on another weekend call out.
"Our best wishes go to the casualty and hopefully he will make a speedy and full recovery."