Xenophilus was a Pythagorean philosopher and musician who lived during the 4th century BCE. Ancient sources describe him as coming from Chalcidice or possibly Thrace. He is noted for his exceptionally long life, reportedly reaching 105 years old. He was a student of the earlier Pythagorean Philolaus and, importantly, the teacher of Aristoxenus of Tarentum, who later studied under Aristotle. This connection made Xenophilus a bridge between the Pythagorean tradition and the emerging Peripatetic school of Aristotle.

No writings by Xenophilus survive, and he is known only from mentions in later biographical accounts. According to modern scholars, his teachings—particularly on music theory and harmonics—were likely passed on orally or through the work of his students. His most famous pupil, Aristoxenus, went on to write foundational works on musical science, which were influenced by this early Pythagorean training.

Xenophilus’s primary historical importance lies in this role as a teacher and link in a philosophical chain. He represents a direct point of transmission for Pythagorean ideas about mathematics, music, and lifestyle into later Greek thought. Furthermore, his reported longevity was frequently cited in antiquity as evidence for the health benefits of the disciplined Pythagorean way of life.