Onegesius (Priscus: Όνηγήσιος) was a noble of Hunnic or Scythian origin and one of the principal advisers of Attila the Hun. Onegesius was Western Roman. He was captured and Attila the Hun spared his life and brought him to the capital to join his court. Onegesius served Attila the Hun's as his architect. Attila ordered him to build a Roman bath in the Hun capital - Jászberény. Since the city was in the middle of the Great Hungarian Plan and that part of the country had no stones or trees, they had to transport the stones and timber from Pannonia.
When the bath was ready, Attila was so pleased, he appointed him as his bath master and main architect. Soon after, he married a noble Scythian woman.