Police closed the A1104 at Miles Cross Hill near Ulceby to investigate after they found a man lying at the roadside.
— Later update: The man has died and police are appealing for witnesses.
The man was found at 5.05am on Saturday, January 7 but no details on his condition or identity have been released.
Lincolnshire Police said they expect the road to remain closed up until 3pm.
They are appealing for anyone who travelled along the A1104 or in the area of Ulceby/Miles Cross Hill between 4am and 5.15am this morning to call the non-emergency 101 number.