A protectorate was an administrative unit within the Republic of Cinnabar sphere of influence, usually designating a nation with partial autonomy.

By 5147 CE both Alliance of Free Stars and Cinnabar controlled multiworld empires which were held together by self-interest. The star systems of Cinnabar's protectorates had no external political authority, but the local magnates could move to Cinnabar and gain a degree of influence over the affairs of the whole Republic. Protected worlds were in a position clearly inferior to that of Cinnabar itself, but with equal clarity they were better off than they would have been if fully independent.1:2

They were typically governed by Residents, and protected by the Protectorate Service of Republic of Cinnabar Navy.6:9