The work will affect trains on Saturday and Sunday (January 25 and January 26).
We have compiled all the details for you to plan your weekend.
Engineering work is taking place between London Bridge, New Cross Gate and Tulse Hill via Peckham Rye, closing all lines.
All day on Saturday and Sunday, replacement buses will run between London Bridge and Tulse Hill via Peckham Rye.
No Southern trains will run between London Bridge and Sydenham.
Saturday (January 25):
Services to and from Uckfield will run between East Croydon and Uckfield only.
Services to and from Beckenham Junction will run between Tulse Hill and Beckenham Junction only.
Services between London Bridge and London Victoria will run between Crystal Palace and London Victoria only.
Services between London Bridge and Epsom will be diverted to run between London Victoria and Epsom.
An alternate train service will run between Tulse Hill and Caterham and Tattenham Corner.
Saturday and Sunday (January 25 and January 26):
Engineering work is also taking place between Littlehampton and Barnham, Bognor Regis and Chichester, closing all lines.
All day on Saturday and Sunday, buses will replace trains between Littlehampton and Barnham, Bognor Regis and Chichester.
Also, no trains will run between Havant and Southampton Central.
Services between London Victoria and Portsmouth Harbour via Horsham will be diverted to run between London Victoria and Littlehampton via Horsham.
Services between Brighton and Littlehampton will run to an amended timetable.
An alternative train service will run between Chichester and Portsmouth Harbour.
Engineering work is also taking place between Bexhill and Ashford International, closing all lines.
All day on Saturday and Sunday, buses will replace trains between Bexhill and Hastings, Ore, and Ashford International.
Train services between London Victoria, Brighton Eastbourne and Bexhill will run to an amended timetable.
