A casualty on the tracks was reported at Hanwell station at around 1.15pm today (January 10).
Officers and London Ambulance Service crews attended, and the person was pronounced dead shortly after.
The incident is not being treated as suspicious and a file will be prepared for the coroner.
All lines between London Paddington and Reading have been closed as the incident is being dealt with.
Major disruption is expected until 4.30pm.
If you need someone to talk to, Samaritans are available to contact any time day or night on 116 123.
A spokesperson for British Transport Police said: “Officers were called to Hanwell railway station at around 1.15pm today (10 January) following reports of a casualty on the tracks.
“Paramedics also attended, however sadly a person was pronounced dead at the scene.
“The incident is not being treated as suspicious and a file will be prepared for the coroner.”
