British Transport Police (BTP) were called to Ravensthorpe station shortly after 4.20pm and officers attended with paramedics.
In a statement, the BTP said: “Work is now being done to identify the woman and inform her family.
“Officers remain on scene and are making enquiries to establish how the woman came to be on the tracks.
“A file will be prepared for the coroner.”
Train services have been severely affected, with some Northern and TransPennine Express services travelling between Huddersfield and Leeds delayed by up to 60 minutes, cancelled or diverted.
The disruption is expected to continue for the rest of the day.
Buses are running between Huddersfield and Leeds, and from York and Scarborough to supplement TransPennine Express services.
TransPennine Express customers can use Virgin Trains East Coast services between Leeds and Newcastle instead.