The work will affect trains between January 4 (Saturday) and January 5 (Sunday).
We have compiled all the details on these works so that you can plan your journey this week.
Saturday (January 4):
Engineering work is taking place overnight between Arundel, Angmering and Littlehampton and Barnham, closing all lines.
The 11.16pm train from London Victoria to Chichester train will terminate at Angmering.
A replacement bus will run from Angmering to Chichester.
Sunday (January 5):
Engineering work is taking place between New Cross Gate, Crystal Palace and West Croydon, closing all lines.
At 12.40am, the London Victoria to Norwood Junction train will terminate at Crystal Palace.
A replacement bus will run from Crystal Palace to Norwood Junction.
Replacement buses will run between New Cross Gate and Crystal Palace all day on Sunday.
Trains will run between London Victoria and Crystal Palace via West Norwood.
Trains between London Bridge, Caterham and Tattenham Corner will run to an amended timetable and will be diverted via Tulse Hill.
Buses will also replace trains between Epsom and Dorking.
Engineering work is taking place until approximately 9.20am between Willesden Junction and Watford Junction, closing some lines.
Until around that time on Sunday morning, no Southern trains will run between Clapham Junction and Watford Junction.
