The female driver and her male passenger, believed to have been in their early 20s, died in the crash on Runshaw Lane, Euxton, at about 23:00 GMT on Thursday.
The Fiat Punto, travelling towards Leyland, came off the road close to the Plough Inn, police said.
Both victims suffered fatal head injuries and died at the scene.
Lancashire Police is appealing for witnesses to come forward.
Sgt Malcolm Bell said: "We would be particularly keen to speak to anyone who saw the car before the incident, or witnessed the accident."
A man and a woman were killed when their car lost control and collided with a tree in Lancashire.