The Shenfield–Southend line is a branch line off the Great Eastern Main Line in Essex, in the east of England. It links Shenfield in the west to Southend Victoria, in Southend-on-Sea, in the east. The vast majority of services connect to or from the Great Eastern Main Line and its London terminus at Liverpool Street.

The Great Eastern Main Line is a 114.5-mile (184.3 km) major railway line on the British railway system which connects Liverpool Street station in central London with destinations in east London and the East of England, including Shenfield, Chelmsford, Colchester, Ipswich and Norwich. Its numerous branches also connect the main line to Southminster, Braintree, Sudbury, Harwich and a number of coastal towns including Southend-on-Sea, Clacton-on-Sea, Walton-on-the-Naze and Lowestoft.