Breakaway Roman state founded by the general Postumus during the Crisis of the Third Century, at its height (260-269) controlling Gaul, Germania, Britannia and Hispania as a functioning separate administration with its own emperors, army and coinage, without ever attempting to seize Rome itself.
Contracted after Postumus's assassination in 269 (Hispania and part of Gaul returned to central Roman control); the rump state under Tetricus I was defeated by Emperor Aurelian at the Battle of Châlons in 274 and reincorporated into the Roman Empire.
The standard scholarly monograph on the Gallic Empire's political history and institutions.
Broad context on the Crisis of the Third Century within which the Gallic Empire arose.