Eunapius of Sardis was a Greek author and teacher who lived during the 4th and 5th centuries CE, a period of transition known as Late Antiquity. He was born around 347 CE in Sardis, in Lydia. A committed pagan in an increasingly Christian Roman Empire, he was educated as a Neoplatonist philosopher and worked as a teacher of rhetoric and a physician.

His surviving work is the Lives of the Philosophers and Sophists, a collection of biographies of important pagan philosophers and teachers from the 4th century. This book is a crucial primary source for modern scholars, offering a contemporary pagan perspective on major figures and detailing the practices of theurgic Neoplatonism, a mystical philosophical tradition. Eunapius also wrote a Universal History, which is now lost except for fragments. This history was openly critical of Christian emperors and favorable to the pagan emperor Julian. According to modern scholars, this lost work was highly influential, serving as a major source for later historians and shaping the narrative of the period's religious conflicts for centuries.

Eunapius's writings provide an invaluable window into the world of late antique pagan intellectuals as they witnessed the decline of traditional Greco-Roman religion and culture.