Emergency services were sent to the accident near Gatehouse of Fleet at about 11:50.
Police said a 76-year-old man driving a Renault Scenic died at the scene of the crash.
The road was closed for several hours while collision investigation work continued and a lengthy diversion route put in place.
Drivers were advised to avoid the area if at all possible.
Anyone with information about the crash has been asked to contact police.
An elderly man has died in a single-vehicle crash on the A75 in Dumfries and Galloway.