The week-long industrial action has come after weeks of disruption as a result of a revised timetable which cut more than 340 trains and with the further threat of strike action continuing into September.
Some routes will not be served at all while others will be affected by severe delays. The travel advice from Southern is don't travel unless necessary, and if you do, check live timetables online.
Here's what you need to know about travelling during this week's strikes...
The strike starts at one minute past midnight on Monday and ends at 11.59pm on Friday.
There will be NO service running from....
- Clapham Junction to Milton Keynes via Kensington Olympia
- Dorking to Horsham
- Oxted in Uckfield
- Haywards Heath to Lewes
- Preston Park to Hove
- Lewes to Seaford (bus replacement service)
- Eastbourne to Ashford International via Hastings (bus replacement)
- Chichester to Portsmouth Harbour and Southampton Central
- Redhill to Tonbridge
- Redhil to Reigate
- Earlswood, Salfords and Faygate stations
- Guildford to Leatherhead
- Sutton to Streatham via Wimbledon
- Crystal Palace to Beckenham Junction
- West Norwood to Tulse Hill
Stations may be served by other operators, however they may be more busy.
There are some services running from 7.30am until 6pm, but they are limited to around two per hour and Southern warns these will also be extremely busy. They are:
London Bridge to East Grinstead (calling at Norwood Junction, East Croydon, Sanderstead, Riddlesdown, Upper Warlingham, Woldingham, Oxted, Hurst Green, Lingfield, Dormans)
London Victoria to Three Bridges (calling at Clapham Junction, East Croydon, Redhill, Gatwick Airport)
Three Bridges to Chichester (calling at Crawley, Ifield, Littlehaven, Horsham, Christs Hospital, Billingshurst, Pulborough, Amberley, Arundel, Ford, Barnham)
Brighton to Bognor Regis (calling at, Hove, Aldrington, Portslade, Fishersgate, Southwick, Shoreham, Lancing, East Worthing, Worthing, West Worthing, Durrington, Goring, Angmering, Littlehampton, Ford, Barnham, Bognore Regis)
Brighton to Eastbourne (calling at London Road, Moulescoomb, Falmer, Lewes, Glynde, Berwick, Polegate, Hampden Park)
Exact timetables for each of these routes can be found here.
Dorking, Epsom, Sutton and London Bridge to London Bridge and London Victoria
Normal services (but busy)
Tattenham Corner, Caterham, Epsom Downs to London (although, Southern says there may be potential disruption)
Purley, Croydon to London Bridge and London Victoria
(click or tap the map to zoom in)