The incidents took place in the Spalding and Anwick areas, the county’s police force said today.
A 20-year-old woman died when her blue Renault Clio car was in collision with an HGV on the A16 near Spalding shortly after 4pm yesterday.
The driver of the Fleet Hargate-based Scania HGV was uninjured.
In the second incident, a 23-year-old pedestrian died when he was hit by a Volvo HGV on the A153 between Anwick and Speedway Corner, near Ruskington, just before 2.10am today.
The dead man was from the local area while the 32-year-old HGV driver, who was uninjured, is from Ruskington.
Police are appealing for witnesses to both incidents.