Flooding on the line has brought trains to a standstill.
Southern services are not running between Ore, near Hastings, and Ashford this afternoon.
The operator says heavy rain has led to floodwater on the tracks.
There are also delays of 20 minutes due to a speed restriction between Eastbourne and Hastings.
A Southern spokesperson said on X: “We have been told about heavy rain flooding the railway between Hastings and Ashford International.
“As a result of this incident, trains are being affected in two ways.
“A speed restriction will delay trains between Eastbourne and Hastings.
“No trains can run between Ore and Ashford International.
“Your journey in this area will be heavily delayed, and you may need to use an alternative route.”
Replacement buses have been requested and are on their way to Ashford and Hastings.
Train tickets can be used at no extra cost on Stagecoach services 500, 511, 511a, 511b between Ashford International and Ham Street, 101 and 100 between Hastings and Rye and 99 between Eastbourne and Hastings.
