Ocellus of Lucania is the name given to an early Pythagorean philosopher traditionally placed in the 6th or 5th century BCE. He is associated with Lucania, a region in southern Italy where the Pythagorean school was active. However, no reliable historical details about his life are known.

The primary work connected to his name is On the Nature of the Universe, a complete treatise that argues for the eternal existence of the cosmos and discusses the soul and reproduction. According to modern scholars, this text is a pseudepigraph, meaning it was not actually written by the early Pythagorean Ocellus. It is generally dated to the Hellenistic period, centuries after his traditional lifetime. Two other lost works, On Law and On Kingship, are also attributed to him in later traditions.

The significance of Ocellus lies in the influence of the text attributed to him. Although not authentically ancient, On the Nature of the Universe was received in later antiquity as a key Pythagorean document. It was cited and debated by important figures like the Christian philosopher Origen and the Neoplatonist Proclus. The work was later translated into Arabic and Latin, ensuring its place in the history of ideas about the eternity of the world. The figure of Ocellus thus represents how later eras constructed and used the authority of early Pythagorean thinkers.