UK-based train operator South West Trains has resumed full service between Eastleigh and Fareham through Hedge End and Botley on 15 March.
The move comes after the completion of repairs to landslip, which was the largest of three to happen on the railway near Botley in Hampshire on 1 February, following five months worth of rain in December and January.
Network Rail said that the largest slip site near Botley saw an 80m-long and 15m high length of embankment fail.
A team of 100 engineers worked at the site round the clock to restore the vital line that links Fareham with Eastleigh.
The new road built to access the sites was around 2km and around 20,000 tons of new material was used to rebuild the Botley line that was originally constructed in the 1840s.
Trains from Portsmouth to London Waterloo were diverted, with buses serving stations from Fareham to Eastleigh during the Botley line closure.
South West Trains-Network Rail alliance managing director Tim Shoveller said: "Despite some very challenging conditions, our engineers have done a great job of re-building the railway around Botley in just a few weeks, which is testament to their hard work and commitment.
"We are pleased to be able to fully re-open the line from Saturday morning and re-instate our normal service for passengers."