Aristoxenus of Tarentum (4th century BC) was a Greek peripatetic philosopher, and writer on music and rhythm.

He was taught first by his father Spintharus , a pupil of Socrates, and later by the Pythagoreans, Lamprus of Erythrae and Xenophilus , from whom he learned the theory of music. Finally he studied under Aristotle at Athens, and was deeply annoyed, it is said, when Theophrastus was appointed head of the school on Aristotle's death.

His writings, said to have numbered four hundred and fifty-three, were in the style of Aristotle, and dealt with philosophy, ethics and music. The empirical tendency of his thought is shown in his theory that the soul is related to the body as harmony to the parts of a musical instrument. We have no evidence as to the method by which he deduced this theory (cf. Theodor Gomperz, Greek Thinkers, Eng. trans. 1905, vol. iii. p. 43).

In music he held that the notes of the scale are to be judged, not as the Pythagoreans held, by mathematical ratio, but by the ear. The only work of his that has come down to us is the three books of the Elements of Harmony, an incomplete musical treatise. Grenfell and Hunt's Oxyrhynchus Papyri (vol. i., 1898) contains a five-column fragment of a treatise on metre; probably this treatise of Aristoxenus.