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 line was worked by the LSWR as part of its own system, but the PD&SWJR adopted the East Cornwall Mineral Railway which connected Kelly Bray and Calstock, and connected it to the main line at Bere Alston. This became the Callington branch, and the PD&SWJR operated the line itself through a subsidiary company.
In the 1960s, the main line from Lydford closed, as did the western end of the Callington line, but the section from St Budeaux to Gunnislake remains open and the passenger operation is known as the Tamar Valley Line.