ONESIMUS. - A fugitive slave, probably a Phrygian from Colossae (Col. 4:9), on whose behalf St. Paul wrote the Epistle to Philemon (q.v.). The name Onesimus (= "Useful") was very common among slaves, almost as if to indicate the purpose of their existence. After his conversion, he was mentioned in the letter to Philemon. Paul presents him, with pride, to the community of Colossae as a "faithful and beloved brother" (Col. 4:9), and in sending him to Philemon, he assures him that Onesimus, now won for Christ and become a brother, will no longer be the useless (Philem. 16) and, perhaps, the thief (ibid., 19) of former days, but will live up to his name.
Nothing more is known of him from the New Testament. An Onesimus was bishop of Ephesus when St. Ignatius the Martyr wrote to that community (Ad Ephes. 1:3). Indeed, the martyrologies state that the slave converted by Paul succeeded Timothy in that see (Acta SS. Februarii, II, Antwerp 1658, pp. 856 ff.); but the name was so common that one cannot conclude to the identity of the person. The Apostolic Constitutions (7:46: PG 1, 1056), on the other hand, say that he was appointed by Paul himself as bishop of Beren in Macedonia. According to other sources, he would have preached in Spain. The accounts are no more in agreement regarding the place (Rome? Puteoli?), the time (under Nero? Domitian?), and the manner of his martyrdom. Onesimus embodies that social category to which only Christianity has given freedom and dignity. The Latin Church commemorates him on February 16, the Greek Church on February 15.