Emergency services rushed to the Southern Expressway entrance at Bedford Park near Flinders Drive after reports the pedestrian had been hit by a vehicle.
The 23-year-old from Sellicks Beach died at the scene.
The truck driver, a 40-year-old man from Adelaide's northern suburbs, was not injured in the crash.
Police are investigating the circumstances of the crash.
The man's death is the 89th life lost on South Australian roads so far this year, compared to 57 at the same time last year.
