The collision was reported at just after 06:45 BST on the coastbound carriageway close to the slip road at junction eight for Leeds Castle
The coastbound carriageway was closed between junctions eight and nine and reopened at 14:00.
The London-bound carriageway was also closed briefly following the death. Any witnesses are asked to contact police.
A male pedestrian has been killed while walking on the M20 in Kent, police said.