Emergency services were called to the B1183 between Horncastle and Scrivelsby at about 5.50pm after an orange Vauxhall Corsa collided with a tree.
A Lincolnshire Police spokesman said: “We are appealing for witnesses and anyone with dashcam footage following a single car collision on the B1183 near Scrivelsby, Horncastle.
“It was called into Police at 5.49pm on Tuesday, January 22.
“The vehicle involved was an orange Vauxhall Corsa.
“The driver, a 20-year-old woman, was taken to hospital but later died.
“Next of kin are aware and we continue to support them.”
• Anyone who was in the area between about 5.30pm and 5.50pm on Tuesday evening and either saw the collision or saw the orange Vauxhall Corsa before the collision is asked to contact 101 and quote incident 315 of January 22.