It happened shortly after 8.20 am today on the A684 Stokesley Road just outside Northallerton.
The collision involved a green heavy goods vehicle sign written with ABN travelling away from Northallerton and a blue Ford Fiesta travelling along the A684 towards Northallerton.
As a result of the collision the driver of the Ford Fiesta, 19, from the Billingham area, sustained serious injuries.
He has been taken to James Cook hospital for treatment and at this time is seriously ill. The driver of the HGV a male, aged 53, 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 area appealing to anyone who witnessed the collision or the vehicles involved prior to the collision to contact TC161 Steve Wood by calling 101, selecting option 2 and asking for Steve Wood. You can also email Steven.Wood161@northyorkshire.pnn.police.uk. Please quote reference 12180087684.
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.