They say it happened around 02:10, on La Rue De La Petite Falaise in Trinity.
A police statement says that a silver Perodua Kelisa with five people in it, collided with a stationary vehicle.
An 18-year-old passenger was seriously hurt, and is now being treated for head injuries – two other 18-year-old men were also treated in hospital for more minor injuries.
Police are asking anyone who witnessed the crash to get in touch by calling 612612 quoting M02778/2021.