Gardaí attended the scene at approximately 2.50am following reports of an unconscious man lying on the road. The man (age unconfirmed at this time), who was travelling on an electric scooter from the direction of Slane, was treated by ambulance services but was later pronounced dead.
The road is currently closed pending a technical examination by Forensic Collision Investigators. Local diversions are in place.
Gardaí are treating this incident as a possible road traffic collision.
Gardaí at Navan are appealing for any witnesses or for anyone with information to come forward.
Gardaí are also appealing for any road users who may have camera footage (including dash-cam) who were travelling on the N51 in Harmanstown between approximately 1.30am and 3am to make this footage available to them.
Anyone with information is asked to contact the Incident Room at Navan Garda Station on 046 9079930, the Garda Confidential Line on 1800 666 111, or any Garda Station.