The fatal collision was reported at 3.30am on the line near Wigan where the casualty was pronounced dead at the scene.
Emergency services attended and recovered the body whilst enquiries continue this morning to identify the casualty.
A police spokesman said: “British Transport Police were called to the line near Wigan at 3.34am today (21 July) following reports of a casualty on the tracks.
“Paramedics also attended and sadly a person was pronounced dead at the scene.
“Officers are currently working to identify the full circumstances behind their death.”
No further details have been released about the casualty at this stage.
National Rail has advised that delays are expected to services on the line until around 10am.
"A person has been hit by a train between Wigan North Western and Preston, “ said a spokesman. “As all lines are currently blocked, trains may be cancelled or diverted until approximately 10am.
"If you’ve been affected by what happened on the network today, there is always someone to talk to. You can contact the Samaritans on 116 123 from any phone for a confidential chat.”
A number of routes were affected, including:
- the Avanti West Coast between London Euston and Lancaster
- the Caledonian Sleeper between London Euston and Inverness
- the Northern between Manchester Airport and Barrow-in-Furness
North West Ambulance Service were approached for further details.