The Plymouth, Devonport and South Western Junction Railway (PD&SWJR) was an English railway company. It constructed a main line railway between Lydford and Devonport, in Devon, England, enabling the London and South Western Railway (LSWR) to reach Plymouth more conveniently than before.

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.