Shi'ar Ducats were a unit of money that was the official currency of the New Shi'ar Imperium and later used as legal tender under the laws of other governments including the Systems Commonwealth, the Interplanetary Neo-British Kingdom, the Kurgan Caliphate, and the Sontaran Dominion.

There were coins made of metal worth 10 percent, 25 percent, and 75 percent of a Ducat, and plastic bills worth one, five, 10, 25, 75, 100, 1000, and 10,000 Ducats.

Ducats were even represented in a non-physical, electronic form as computer data.

Other units of money included Systems Commonwealth Dollars, Neo-British Pounds, Kurgan Dinars, and Sontaran Credits, but these units of money never came close to completely substituting for Shi'ar Ducats.