The driver of a black Seat Ibiza is reported to have collided with a tree in Dumpton Park Drive near the junction with Bay View Road, at around 3.20am on Sunday 1 October 2023.
Patrols attended the scene along with South East Coast Ambulance Service where a passenger, an 18-year-old man, was confirmed deceased.
The driver was taken to a local hospital where he is being treated for injuries.
Officers from the Serious Collision Investigation Unit (SCIU) are carrying out enquiries and would like to hear from anyone who might have witnessed the incident.
They are also appealing for anyone with relevant dashcam or CCTV footage taken in the area around the time, to come forward.
Witnesses should call the SCIU appeal line on 01622 798538 quoting reference 01-0212. You can also email sciu.td@kent.pnn.police.uk
CCTV and dashcam footage can submitted via the police public portal.