The northbound stretch of the M40 is currently closed from junction 12 (for Gaydon) to 13 (for Warwick) after a four-vehicle collision.
A man in his 20s suffered serious injuries and was taken to hospital for treatment.
Officers were called to the northbound carriageway at around 10.15pm last night (Tuesday November 19) and are still at the scene.
A police spokesperson said: "The northbound stretch is currently closed from junction 12 (for Gaydon) to 13 (for Warwick) and the carriageway is expected to remain so until later this morning with motorists advised to follow diversions and take an alternative route where possible.
"Traffic is being diverted via the B4100 and A452, to rejoin the M40 at junction 14.
Sergeant Darren Kearns from Warwickshire Police said: "We appreciate this incident will cause significant disruption for motorists this morning and we would ask that they please be patient and bear with us while we deal with the incident.
"As I'm sure the public can understand, we are in the process of investigating a serious collision. This will require a detailed investigation which may take a number of hours to complete.
"We are working with partners to ensure the road is open as soon as possible and are doing all we can to minimise closure times.
“We are also sending officers to the surrounding areas to ensure those who may be caught up in the traffic can be on their way as soon as possible.
"We would like to thank everyone for their support and understanding at this time."
Please see here for diversions or follow Highways England's Twitter @HighwaysWMIDS
Officers are also appealing for anyone who saw the collision or has dashcam footage to get in touch. Anyone with information is asked to call Warwickshire Police on 101 quoting incident 423 of 19 November.