Ammonius of Alexandria was a Neoplatonic philosopher who lived and taught in the late 5th and early 6th centuries CE. He was the son of philosophers and, after being educated under Proclus in Athens, returned to Alexandria to lead its Neoplatonic school. His leadership occurred during a period of growing Christian authority. According to historical accounts, Ammonius made a pragmatic agreement with the local Christian patriarch to ensure his school's survival, allowing it to continue operating longer than the pagan school in Athens.

He was a renowned teacher whose students included several important later philosophers. Ammonius is known almost entirely through commentaries on Aristotle's works, which were compiled from his lectures by his students. Extant works attributed to his teaching include commentaries on Aristotle's Categories, Prior Analytics, and On Interpretation. The attribution of some texts, such as a commentary on Porphyry's Isagoge, is less certain and may be the work of his students.

His primary significance lies in his role as an educator and systematizer. Ammonius helped establish a standard curriculum focused on explaining Aristotle's logic and physics within a Neoplatonic framework. By training a generation of influential thinkers and ensuring the survival of his school, he played a key role in transmitting classical Greek philosophy, particularly Aristotelian studies, into the Byzantine and later scholarly traditions.