The clockwise M25 is shut between J10 at the A3 Wisley Interchange to J11 at the A320 St Peters Way. The incident took place at around 3.30am and involved a lorry and a car, traffic firm Inrix said.
Tailbacks of half-an-hour have been reported back to J9.
Inrix said: “M25 clockwise closed, queueing traffic for four miles due to accident investigation work from J10 A3 (Wisley Interchange) to J11 A320 St Peters Way (Chertsey).
“Congestion to just before Cobham Services located between J9 and J10 taking around 30 minutes.
“The road has been closed since around 03:30 following a serious accident involving a lorry and a car.”
This is a developing news story, more to follow.