Almost half of the platforms at Waterloo Station will be shut for three days this Christmas to allow track to be replaced.
On Friday 27, Saturday 28 and Sunday 29 December platforms 1-9 at Waterloo Station will be out of use due to major engineering works.
A reduced train service will run to and from those platforms which remain open.
Some services will start from stations away from London Waterloo and passengers may have to change trains to complete their journeys.
"With more than 100 million passengers a year travelling through Waterloo Station there is never a good time to carry out work which affects the level of service we can provide," said Tim Shoveller, managing director of the Network Rail and South West Trains Alliance.
"However, we normally see around half the number of passengers travelling over Christmas than at other times of the year, so it provides a good opportunity to carry out much needed improvement work on the track on the busy approach to the Waterloo Station.
"This will provide a more reliable infrastructure which will help to deliver a better level of service to passengers.
"Since the start of the alliance, we have hugely increased the amount of maintenance on our network and are now investing an extra £3 million a year to improve the quality of the infrastructure on the UK's busiest commuter network.
"At the same time, we are pushing ahead with plans to significantly improve the infrastructure around Waterloo station by extending existing platforms and bringing all of the former international platforms back into use."
A 350 tonne road crane will be used to lift pre-built sections of track onto the railway. The track will then be moved into place using a crane operated from on the railway. The old track will be removed from the work site by an engineering train.
Tim Shoveller added: "Using a road crane to lift pre-built sections of track onto the railway is part of the alliance's efforts to complete the work as quickly as possible and keep disruption to a minimum.
"We are committed to improving the network and will continue to invest in Waterloo Station and the track on the approach to provide a better railway for passengers."