 Although Rome ruled over an empire long before Cicero died, and the republican constitution that he had served would remain formally intact in many respects long after that date as well, the imperial era of Roman government is standardly associated with the elevation of Octavian by the Senate in 27 BCE by according him the title of “Augustus” (among other novel titles and combinations of offices that he was then and later accorded). Octavian and a number of his successors were also referred to as the princeps, literally the first man, implicitly the first among nominal equals, sometimes translated by the English derivation ‘prince’, and so giving rise to the description of the period from 27 BCE–284 CE as the Principate (to be followed in turn by the Dominate). In this period, Stoicism continued to exercise an important hold, drawing in part on the Hellenistic genre of advice to kings; Platonism too, and forms of Pythagoreanism, regained much sway. Moreover, a number of Stoic-minded writers and orators played their parts in Roman political life, some fashioning the life of a philosopher itself into a distinctive form of what might be called non-political politics (Trapp 2007). In this article, I cannot explore the full ramifications of these philosophical developments under the Empire, in writers in Greek as well as in Latin, and influencing not only pagan but also Jewish and Christian thinkers. The article also leaves aside the many and varied important contributions to political thought in Rome and its possessions made not by philosophers but by historians, including Livy, Sallust, Diodorus Siculus, Tacitus, and Suetonius. (Again, for an overview that seeks to integrate political and historical developments with political theorizing, see J.W. Atkins 2018.)