The woman had to be cut from her car by Fire and Rescue Service officials after her grey VW Golf GTI collided with a bank at the junction of Haute Croix around 03:45.
No one else was in the car or involved in the crash.
Pictured: The collision happened in the early hours of Monday (16 March) at the Haute Croix junction in Trinity.
She was subsequently taken to A&E and remains in hospital with serious injuries.
Police are now investigating the crash and are urging witnesses or those with more information to urgently come forward.
They can call Police on 612612 or make an anonymous report via Crimestoppers’ online form.