Themistius (317, Paphlagonia — c. 390 CE, Constantinople) is a statesman, rhetorician, and philosopher.

He flourishes in the reigns of Constantius II, Julian, Jovian, Valens, Gratian, and Theodosius I; and he enjoys the favor of all those emperors, notwithstanding their many differences, and the fact that he himself is not a Christian.

He is admitted to the senate by Constantius in 355, and he is prefect of Constantinople in 384 on the nomination of Theodosius.

Of his many works, thirty-three orations of his have come down to us, as well as various commentaries and epitomes of the works of Aristotle.