British Transport Police (BTP) confirmed officers and paramedics were called to the railway line near Redhill shortly after 12.10pm on Thursday, following reports of a casualty on the tracks.
“Sadly a person was pronounced dead at the scene,” said a spokesperson.
“This incident is not being treated as suspicious and a file will be prepared for the coroner.”
National Rail warned “major disruption” was expected until 4pm, affecting Gatwick Express, Great Western Railway, Southern and Thameslink trains.
“A person has been hit by a train between East Croydon and Gatwick Airport,” said National Rail’s website on Thursday afternoon.
“As all lines are currently closed, trains may be cancelled, delayed by up to 90 minutes or revised.
“Major disruption is expected until 4pm.”
Thameslink, Southern and Gatwick Airport trains are not able to run between East Croydon or Redhill and Gatwick Aiport.
National Rail said: “Some trains will terminate before they get to the area, and others will be severely delayed or cancelled.
“Where possible, shuttle trains will run between the South Coast and Gatwick Airport, and a limited number of trains will also be able to run between East Croydon and London.
“This will also cause major disruption to trains through Central London on the Thameslink network.”
Great Western Railway trains are also being affected. They may start and terminate from Redhill, but will not call at Gatwick Airport.
Tickets are being accepted on alternative services.
For more information, visit the National Rail website.
Help can be reached for free through the Samaritans on 116 123 or at jo@samaritans.org. For more information on finding help, the NHS has a range of services.
