The Southern Railway (SR), sometimes shortened to 'Southern', was a British railway company established in the 1923 Grouping. It linked London with the Channel ports, South West England, South coast resorts and Kent. The railway was formed by the amalgamation of several smaller railway companies, the largest of which were the London and South Western Railway (LSWR), the London, Brighton and South Coast Railway (LB&SCR) and the South Eastern and Chatham Railway (SE&CR). The construction of what was to become the Southern Railway began in 1838 with the opening of the London and Southampton Railway, which was renamed the London & South Western Railway.

The London and South Western Railway was a railway company in England from 1838 to 1922. Originating as the London and Southampton Railway, its network extended to Dorchester and Weymouth, to Salisbury, Exeter and Plymouth, and to Padstow, Ilfracombe and Bude. It developed a network of routes in Hampshire, Surrey and Berkshire, including Portsmouth and Reading.