A young male passenger has died following a single-vehicle crash into a tree in the Royal National Park on Saturday afternoon.
Emergency services were called to Lady Wakehurst Drive at Lilyvale, near Helensburgh, about 1.45pm to reports of crash.
On arrival, officers from Wollongong Police District located a male passenger, aged 19, deceased. He has not been formally identified.
The 18-year-old male driver was treated at the scene and taken to St George Hospital in a stable condition with hip and arm injuries as well as grazes.
He will undergo mandatory testing.
As of Sunday, the teen remains in a stable condition in hospital.
Both boys were from the Fairfield area.
NSW Ambulance, Duty Operations Manager, Inspector Matt Sterling said "it was such a distressing scene to arrive at".
"Paramedics attempted to treat the man, but tragically, there was nothing they could do," he said.
"This is absolutely horrific - it is such a tragedy to lose such a young life.
"Our thoughts are with the man's family and friends, as well as those first responders who attended the scene - it is never easy."
A crime scene has been established with officers from the Crash Investigation Unit looking into the circumstances surrounding the incident.
Lady Wakehurst Drive is closed in both directions and people are advised to avoid the area.
The northbound diversion is via Sir Lawrence Hargrave Drive from Bald Hill. Southbound diversion is via McKell Avenue to the Princes Highway.