The Gemon-4 was a capital-scale ion engine manufactured by Cygnus Spaceworks. Four Gemon-4 ion engines were used for emergency or supplementary sublight drives on Imperial-class Star Destroyers and three Destroyer-I ion engines served as main engine units.
- Star Wars: Episode IV A New Hope (First appearance)
- Operation: Elrood
- Star Wars: Episode V The Empire Strikes Back
- Star Wars: Episode VI Return of the Jedi
- The Essential Guide to Vehicles and Vessels (First identified as Gemon-4 ion engine)
- The Galactic Empire—Ships of the Fleet