The London, Chatham and Dover Railway was a railway company in south-eastern England created on 1 August 1859, when the East Kent Railway was given parliamentary approval to change its name. Its lines ran through London and northern and eastern Kent to form a significant part of the Greater London commuter network. The company existed until 31 December 1922 when its assets were merged with those of other companies to form the Southern Railway as a result of the grouping determined by the Railways Act 1921. The railway was always in a difficult financial situation and went bankrupt in 1867, but was able to continue to operate. Many of the difficulties were caused by the severe competition and duplication of services with the South Eastern Railway (SER). However, in 1898 the LCDR agreed with the SER to share the operation of the two railways, work them as a single system and pool receipts: but it was not a full amalgamation. The SER and LCDR remained separate companies with separate shareholders until both becoming constituents of the Southern Railway on 1 January 1923.

The South Eastern Railway (SER) was a railway company in south-eastern England from 1836 until 1922. The company was formed to construct a route from London to Dover. Branch lines were later opened to Tunbridge Wells, Hastings, Canterbury and other places in Kent. The SER absorbed or leased other railways, some older than itself, including the London and Greenwich Railway and the Canterbury and Whitstable Railway. Most of the company's routes were in Kent, eastern Sussex and the London suburbs, with a long cross-country route from Redhill in Surrey to Reading, Berkshire.