Kemp Town branch line was a railway line running from Brighton to Kemptown in England. It operated between 1869 and 1971. It ran from a junction off the Brighton to Lewes line between London Road and Moulsecoomb stations, to Kemp Town railway station. It opened in 1869 and was expensive to construct, requiring a tunnel and a large viaduct.

The passenger service declined after 1917 due to tramway competition, and ceased at the end of 1932, but goods trains continued to operate on the line until 1971.

For a time during the Second World War the tunnel on the branch was used for night storage of main-line passenger stock, as a precaution against bomb damage from enemy action.

Pre-grouping, the line was operated by the London, Brighton and South Coast Railway. Post-grouping it was operated by the Southern Railway then the Southern Region of British Railways.

The railway line from Brighton to Lewes was authorised under the Brighton, Lewes and Hastings Railway Act 1844 (7 & 8 Vict. c. xci), and it was opened on 8 June 1846.

On 27 July 1846, royal assent was given to the act of Parliament authorising the merging of the London and Brighton Railway and the London and Croydon Railway, forming the London, Brighton and South Coast Railway (LBSCR).

The LBSCR became dominant in the Brighton area, but in 1863 a nominally independent company encouraged by the London, Chatham and Dover Railway promoted a line from near Beckenham through East Grinstead to Lewes, and intended to terminate in Brighton at the Kemp Town district. Kemp Town was a quality residential area built in the Regency style by the developer Thomas Read Kemp in the 1820s.

The line was stated to be likely to cost more than £4 million and to require over six miles (9.7 km) of tunnelling.