Officers were called at 7.37pm yesterday (December 29) to reports of a collision involving a brown Peugeot car and the central reservation of the M27 between junction 8 and junction 9.
The driver of the Peugeot, a 41-year-old man, is then believed to have exited his car and walk across the westbound carriageway where he was involved in a collision with a royal mail lorry.
The 41-year-old man was pronounced dead at the scene. His next of kin have been informed and are being supported by specialist officers.
The lorry driver was uninjured.
Investigations into the exact circumstances of the collision are ongoing at this time and the M27 has been fully reopened.
We are keen to speak to any motorists who were driving along this stretch of the M27 at around the time of the incidents and may have seen anything or has dash cam footage.
Anyone with information about this incident is asked to call us on 101, quoting 44200499198.