The Sussex Fortress Royal Engineers was a Territorial Force (TF) unit of Britain's Royal Engineers from 1908 to 1920. As well as coastal defence duties during World War I, the unit provided works companies for service on the Western Front.

The 1st Sussex Engineers was a Volunteer unit of Britain's Royal Engineers raised in Eastbourne in 1890. It became the engineer component of the 44th Division of the Territorial Force, but its units saw action with Regular Army formations on the Western Front, at Salonika and in Italy during the First World War, and in North Russia and Turkey after the war ended. During the Second World War, its units were in the Battle of France and at Alamein, in Sicily, on D Day and the subsequent campaign in North West Europe, including the Rhine crossing. Detached companies fought in Tunisia, Italy, and Burma, where one was involved in the decisive Battle of Kohima and the assault crossing of the Irrawaddy. The unit continued in the postwar Territorial Army until 1967.