A second man is in hospital after the collision on Saturday night.
A white Ford Transit Connect van was travelling along Thorney Leys in Witney, it left the carriageway at around 9.40pm and crashed into an area of trees and bushes near to B&Q.
Paramedics attended the scene but sadly a man in his twenties from Carterton, was pronounced dead at the scene.
Thames Valley Police said his next of kin have been informed and his family are being supported by specially trained officers.
A second man is currently receiving treatment at hospital, his injures are not believed to be serious but he is being kept in for observation.
A 23-year old man, of no fixed address, has been arrested on suspicion of causing death by dangerous driving, in connection with the incident.
Senior investigating officer, Sergeant Mark Scully of the Joint Operations Road Policing Unit, based at Bicester, said: “This collision has sadly led to the death of a man in his twenties. Our thoughts are with his family at this difficult time.
“We are investigating the circumstances of this collision and we are appealing for witnesses to come forward.
“We are keen to speak with anyone who may have seen the collision or that might have seen the white van prior to the collision.
“Additionally we are asking any motorists who were travelling along Thorney Leys at around the time of the incident to please check their dash-cam footage and get in touch if it shows the incident or the white van prior to the incident.“