Kent Police have said the pedestrian was pronounced dead at the scene. The clockwise carriageway of the M25 between junctions 3 and 4 is likely to remain closed until around 11am.
Any witnesses or anyone with information are asked to contact Kent Police on 01622 798538.
More top news
A 24-year-old man has appeared in court this morning after a fatal hit-and-run of a 58-year-old man in east London.
Fifty people had to be evacuated from a three storey block of flats after fire broke out in its roof.
Two people had their lives saved by a smoke alarm after fire ripped through their house in south west London.