The northbound carriageway between junction 11 for Banbury, Oxfordshire and junction 12 for Gaydon, Warwickshire was shut at 11:20 BST.
One person was declared dead at the scene while another was taken to Coventry and Warwickshire Hospital with non-life threatening injuries.
The road was closed for much of the day while investigations were carried out but all lanes have since reopened.
Ambulance crews from the West Midlands and South Central Ambulance Services attended the scene. An air ambulance also attended.
Queues of about four miles were reported on the northbound carriageway before junction 11.
One person has died in a collision between a car and a lorry on the M40.