How will your journey be affected?
Waterloo mainline station is set to go through some major rebuilding work for nearly the whole of August, passengers have been told to avoid the station.
Passengers have been advised to use a different route, work from home, go on holiday or avoid peak periods from the 5 to the 28 August.
Nine of the 25 platforms will close, up to half of the South West Train (SWT) service will be cancelled on some lines.
Some local stations will also be closed, other stations will get busier and will run fewer trains.
The £800m upgrade to Waterloo and South West were announced last year, however the extent of the disruption to passengers was only revealed on Thursday.
The new upgrade is set to bring faster and frequent services, as well as a new fleet of trains.
Christian Roth, SWT managing director, said: “This is the biggest investment in this railway for decades and will provide a significant increase in capacity for the thousands of passengers who use this railway every day.”
“There will be some short term changes and disruption for passengers, particularly during August.”