Eurytus was a Pythagorean philosopher active in the 5th century BCE in southern Italy. He was a student of Philolaus of Croton, belonging to a later generation of the school after its original communities had dispersed. No writings or specific titles from Eurytus survive; his ideas are known only through reports by later ancient authors like Aristotle.

His historical importance lies in a distinctive method he used to demonstrate the core Pythagorean belief that "all things are numbers." According to ancient accounts, Eurytus would determine the number of an object—such as a man or a horse—by arranging pebbles into the shape of that creature. This was an attempt to give a physical form to the abstract idea that numbers are the essence of reality. Modern scholars see Eurytus as providing a concrete, if simplistic, example of how some Pythagoreans interpreted their central doctrine. His method was famously criticized by Aristotle, who argued it missed the deeper philosophical analogy between numbers and things. Consequently, Eurytus remains a minor but notable figure for illustrating a practical application of Pythagorean number theory and for serving as a point of critique in the development of ancient philosophy.