Xenophilus (Greek: Ξενόφιλος; 4th century BC) of Chalcidice, was a Pythagorean philosopher and musician, who lived in the first half of the 4th century BC.Aulus Gellius relates that Xenophilus was the intimate friend and teacher of Aristoxenus, and implies that Xenophilus taught him Pythagorean doctrine. He was said to have belonged to the last generation of Pythagoreans, and he is the only Pythagorean known to have lived in Athens in the 4th century BC. We learn from Diogenes Laërtius that Aristoxenus wrote that when Xenophilus was once asked by someone how he could best educate his son, Xenophilus replied, "By making him the citizen of a well-governed state." According to Pseudo-Lucian, Aristoxenus is supposed to have said that Xenophilus lived 105 years. Xenophilus enjoyed considerable fame in the Renaissance, apparently because of Pliny's claim that he lived 105 years without ever being sick.