A 20-year-old man suffered a serious head injury when the trail bike he was riding left the road collided with a tree near the Murwillumbah golf course around 1am on Saturday morning.
Police say the accident happened on the road leading to the golf course at Murwillumbah, off Byangum Road.
A neighbour who found the injured man on the ground with with head injuries raised the alarm.
He was treated at the scene by ambulance officers before being conveyed by road to the Gold Coast University Hospital in a serious condition.
Tweed-Byron police are appealing for anyone with information to contact them.