The 78-year-old driver was found unconscious in his car in the village of Glencaple on Sunday morning.
His blue Honda Civic had crashed into a fence on Wardlaw Drive at the junction with Great Eastern Drive.
He was taken to Dumfries and Galloway Royal Infirmary where he later died.
Police said no-one else was in the car and no other vehicles were involved in the crash, which happened at around 9.40am.
Officers are appealing for witnesses.
Sergeant Leigh McCulloch said: “We would like to hear from anyone who may have witnessed this collision.
“It does appear that this was a low speed, one vehicle collision and anyone who can help with any information is asked to call Police Scotland on the 101 number.”