Train services will be revised as Network Rail upgrades the railway at Brookwood, between Farnborough and Woking.
The upgrades, which will take place until January 5, are crucial for the continued safe and reliable running of the railway and will involve 19 engineering trains, two tampers, and a rail-mounted crane.
It means journeys between Southampton Central and London Waterloo will be diverted via Guildford and take 45 minutes longer.
Key upgrades include new switches and crossings at Pirbright Junction, where the line to Aldershot leaves the South West Main Line towards Basingstoke, and 3,000 metres of new conductor rail.
More than 100 new track panels will be installed, covering about 2,000 metres, along with approximately 2,800 new sleepers and 9,450 tonnes of ballast.
Over 5,000 metres of new electrification cabling will also be laid.
Track circuits will be upgraded, and new heating equipment will be installed to prevent points from freezing during winter.
Work to strengthen embankments in the area will reduce the risk of landslips, while drainage improvements between Brookwood and Farnborough will help mitigate flooding.
Mark Goodall, Network Rail’s Wessex route director, said: “We’re urging passengers to plan ahead and check before they travel over the festive period while we carry out these essential improvements to the railway.
“Our teams will be working around the clock to upgrade the railway for the long-term benefit of our passengers, which once complete, will mean smoother and more reliable journeys.
“We know there is never a good time to close the railway. However, the festive period presents us with an opportune time to complete more complex upgrades such as these, as fewer passengers are travelling and the railway is closed on Christmas Day and Boxing Day.
“I would like to thank passengers in advance for their patience and understanding while we complete this work.”
South Western Railway (SWR) services will be altered or diverted, with some journeys taking significantly longer.
Rail replacement buses will operate on various routes, including Basingstoke to Woking on December 15, and Farnborough to Woking on December 23 and 24.
SWR network services will not operate on Christmas Day and Boxing Day.
For full details on how the engineering work will affect journeys, visit southwesternrailway.com/woking-christmas. Passengers are urged to plan ahead and check before travelling.