Kieran Currie, 19, was apparently struck by an eastbound lorry on the A75 Gretna to Stranraer road in Dumfries and Galloway, police said.
The accident happened at about 2.40am on Saturday near Calgow Farm, about a mile east of Newton Stewart.
Mr Currie, who sustained serious head injuries, was taken to Dumfries and Galloway Royal Infirmary for treatment but later died.
It forced the closure of the road for around seven hours to allow for collision investigations, with a lengthy diversion put in place.
Police Scotland are asking anyone with information about the accident to come forward, in particular officers would like to speak with the people travelling in a small blue car who stopped at the scene and offered their help.