Sallustius was a Neoplatonic philosopher who lived in the 4th century CE, during the late Roman Empire. He is known primarily for his association with the Emperor Julian, who ruled from 361 to 363 CE and attempted to revive traditional Roman religious practices. According to modern scholars, Sallustius was likely a friend and possibly a disciple of the emperor, and some sources suggest he may have served in a high administrative office. The precise details of his life, including his birthplace and exact dates, are not well documented.

His sole surviving work is a treatise in Greek titled On the Gods and the Cosmos. This short text is a systematic handbook of Neoplatonic theology and cosmology, dedicated to Emperor Julian. It was written as the Christian church was gaining institutional power, during a period when traditional pagan religion and philosophy were being challenged.

The significance of Sallustius lies in this surviving work. It serves as a concise defense of pagan myth and ritual from a philosophical perspective. The treatise argues that traditional stories and practices hold symbolic and theological truths, offering a reasoned justification for polytheism within the Neoplatonic framework. Academics view the work as an important source for understanding the intellectual climate of the 4th century, capturing a pagan philosophical response to the rise of Christianity. Its survival provides a window into the religious and philosophical debates of late antiquity.