The 19-year-old was driving a blue Ford Fiesta travelling along the A684 Stokesley Road towards Northallerton when he was in collision with a green heavy goods vehicle, travelling in the opposite direction at around 8.20am.
The teenager, from Billingham, was taken to James Cook hospital for treatment and is seriously ill, North Yorkshire Police said.
The driver of the HGV, a 53-year-old man from the Northallerton area, was uninjured but shocked and has been assisting police with enquiries.
The road was closed until 1.30pm to allow emergency services including the Yorkshire air ambulance to deal with the incident and examine the scene.
Police want to hear from anyone who saw what happened or the vehicles before the collision. The HGV was sign written with ABN on it. Officers are particular keen to speak to the occupants of a small white vehicle travelling towards Northallerton on the A684 which arrived on the scene shortly after the collision but left prior to police attending, and may have witnessed what happened.
Contact TC161 Steve Wood by calling 101, selecting option 2 and asking for Steve Wood. You can also email [email protected] Please quote reference 12180087684.