Julian, known historically as Julian the Apostate, was a Roman Emperor and philosopher who lived in the 4th century CE. Born in Constantinople in 331 or 332, he was a member of the imperial family. After a youth spent under supervision, he received an education that secretly drew him toward traditional Greek philosophy and religion, despite his Christian upbringing. He studied Neoplatonism in cities like Ephesus and Athens. In 355, he was appointed a junior emperor (Caesar) and sent to Gaul, where he proved to be a successful military commander. His troops later proclaimed him senior emperor (Augustus) in 360, and he ruled as sole emperor from 361 until his death in 363 during a campaign in Persia.

As emperor, Julian publicly rejected Christianity—which earned him the label "Apostate"—and attempted to restore traditional Roman religious practices. He promoted a philosophically refined form of paganism centered on the sun god Helios. According to modern scholars, his reign represents the last major effort to reverse the Christianization of the Roman Empire.

Julian was also a prolific author who wrote in a classicizing Greek style. His surviving works include philosophical orations like the Hymn to King Helios, numerous letters, and satires such as The Caesars and Misopogon (The Beard-Hater). He also wrote a treatise Against the Galilaeans, which is preserved mostly in fragments through quotations by Christian critics. These writings provide crucial insight into the religious and intellectual conflicts of his time, as well as the ideals of a Neoplatonic philosopher-king. Although his religious revival failed, his works remained important for later pagan and Christian thinkers.