Police were called to the Great Western Mail Line near Swindon at around 2.30pm today (April 5).
Paramedics attended but a person died at the scene. The incident is not being treated by police as suspicious.
Great Western Railway trains from Paddington face cancellation and 60 minute delays for the rest of the day.
A British Transport Police spokesperson said: “Officers were called to the line near Swindon at 2:35pm today (5 April) 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.”
A spokesperson for Great Western Railway said: “A person has been struck by a train in the Swindon area, leading to all lines being blocked.
“It is necessary to bring all trains in the affected area to an immediate stop.
“If you are onboard one of the services in this incident and have been affected by this incident or know someone else who needs support, there is always someone to talk to.
“Contact a Samaritan on 116 123 for free, any time, on any phone.”
