Late 4th-c. bishop of Serdica in Illyricum, founder of the sect of the Bonosianis. We know of him from a letter sent to Archbishop Anisius of Thessalonica and the other Illyrican bishops shortly after the synod of Capua in winter 391–392 and the Council of Milan of 392 De Bonoso. The letter, sometimes attributed to Ambrose F. Cavallera, La lettre sur l’évêque Bonose estelle de saint Sirice ou de saint Ambroise? BLE 21 1920 141-147 or to Pope Siricius Jaffé 261, states that a bishop named Bonosus was denounced at the Synod of Capua because he held that Mary was the mother of other children besides Jesus, rejecting her perpetual virginity Ambr., Inst. virg. 35, 65; Ep. 56a. M. Mercatore’s edition of the work, Sardicensis Bonosus. Appendix ad contradictionem XII anathematismi nestoriani, n. 15 PL 48, 924, confirms Bonosus’s existence. His identification remains uncertain, but he might be indentifited with Bonosus of Naissa Aug., Ep. 292, who did not acknowledge Mary’s virginity after Christ’s birth on this point see the contrasting opinions of J. Zeiller, Les origines chrétiennes dans les provinces danubiennes de l’Empire Romain, Paris 1918 and of Hfl-Lecl. Beyond the Marian heresy, some also attribute to Bonosus the denial of Christ’s divinity M. Mercatore. On this point, later evidence against the Bonosiani is more explicit Alc. Avit., Ep. III; Isid., Vir. ill. 32; Simbolo XI concilio di Toledo; they were also sometimes accused of a trinitarian heresy Genn., Eccl. dogmat. 52; Greg. M. epist. 67. DTC 2, 1027-1031; J.A. de Aldama, La carta ambrosiana “De Bonoso”: Marianum 25 1963 1-22; M.S. Meo, La verginità di Maria nella lettera di papa Siricio al vescovo Anisio di Tessalonica: Marianum 25 1963 447-469; K. Schaeferdiek, Bonosus von Naissus, Bonosus von Serdika und die Bonosianer: ZKG 96 1985 162-178; Marienlexikon 1, 538.