Police were called to reports of a casualty on the tracks around 7.50am today near Wool Railway Station.
Paramedics and fire also attended and the person was pronounced dead on the scene.
The incident is not being treated as suspicious.
Trains from Weymouth to Bournemouth have been cancelled as emergency services are on the scene.
A spokesperson for British Transport Police said: “Officers were called to a report of a casualty on the tracks just before 7.50am today (30 January) near Wool Railway Station.
“Officers and paramedics attended and sadly a person was pronounced deceased. The incident is not thought to be suspicious and a file will be prepared for the coroner.”