Man, 69, dies after driving into tree

A man is dead and a woman in hospital after a single-vehicle accident in Qld's southwest.

A 69-year-old man is dead and his female passenger is in a serious condition after the car they were in hit a tree in Queensland's southwest.

Police say the pair were travelling on the Castlereagh Highway, south of St George when they left the road around 2pm on Friday.

The man was pronounced dead at the scene.

The 67-year-old woman was taken to Dirranbandi Hospital and later airlifted to Toowoomba, where she remains in a serious but stable condition.