Tourist, 38, is in a critical condition at Royal Perth Hospital after a bicycle crash on Rottnest Island

A tourist has been airlifted to hospital with life-threatening head injuries after a serious bicycle crash on Rottnest Island.

Emergency services were called to Digby Drive in the Thompson Bay area about 5pm on Tuesday, following reports an overseas visitor had fallen from her bike.

Police and staff from the Rottnest Island Nursing Post attended the scene, where they found a 38-year-old woman with life-threatening head injuries.

The woman was transported off the island by the RAC Rescue Helicopter and taken to Royal Perth Hospital, where she remains in a critical condition.

Police said investigations into the circumstances surrounding the crash are ongoing.