An 18-year-old Aldinga Beach man has died in a crash on the Dukes Highway at Cooke Plains.
Just after 5.30am, a truck travelling towards Adelaide collided with a ute travelling southeast about two kilometres northwest of Coomandook.
A rescue helicopter was sent to the scene immediately, but the ute's driver died before he could be taken to hospital.
The truck driver received only minor physical injuries.
The highway remained closed between Tailem Bend and Coomandook early on Monday afternoon, as police diverted traffic along the Mallee Highway and Old Dukes Highway while major crash investigators inspected the scene.
As such, motorists should expect delays.
Anyone who witnessed the crash, or saw either vehicle before the accident, should contact Crime Stoppers on 1800 333 000 or at www.crimestopperssa.com.au.
The death was the 102nd on South Australian roads this year, compared with 73 at the same time last year.