A young woman is dead after being struck by two cars north of Adelaide overnight.

SA Police (SAPOL) said officers were called to the North South Motorway at Waterloo Corner about 11:30pm on Saturday.

Police said the woman, a 28-year-old from Prospect, was struck by a Mitsubishi Pajero and a Toyota sedan.

She died at the scene.

Major crash investigators examined the scene for several hours, with the motorway closed to northbound traffic while they worked.

The road has since reopened.

The woman's death takes South Australia's road toll to 67, compared with 63 at the same time in 2020.

SAPOL has urged anyone with information, or who witnessed the crash, to contact Crime Stoppers.