The woman, who has not been named but is in her forties, was on the 7-Stanes circuit at Kirroughtree Forest, near Newton Stewart, on Saturday.
She was thrown over the handlebars of her bike and received head and neck injuries.
The Scottish Ambulance Service called in the Galloway Mountain Rescue Team from their base at Newton Stewart.
They also brought in a Helimed air Ambulance to take the woman, who is on holiday in the area, to hospital. She was tended by other bikers until the arrival of paramedics and the Mountain Rescue team. She was brought to safety from the forest by team member and rushed by air ambulance 60 miles to Dumfries and Galloway Royal Infirmary.
Her injuries were not thought to be life threatening.