The Gallic Empire is the name of a brief period within the Dominate that actually occurred during the Crisis of the Third Century and was defeated by Aurelian in order to regain the Gallic territories which split away. He was victorious. The emperors were as follows:

Postumus (259 AD -- 273 AD)
Laelianus (268 AD) (Usurper)
Marcus Aurelius Marius (268 AD)
Victorinus (268 AD -- 271 AD)
Domitianus (271 AD) (Usurper)
Tetricus I (271 AD -- 273 AD)
Tetricus II (271 AD -- 273 AD)