The Bonosiacs were the followers of Bonosus, a fourth-century bishop from Naissus, whom the Synod of Capua had branded a heretic in 391 or 392. They make an unexpected appearance in sources from the Burgundian, Visigothic, and Merovingian kingdoms (ca. 500 – 636). This article claims that, as a distinct community, the Bonosiacs were never a part of the religious landscape of the sixth- and seventh-century West. Rather, the term “Bonosiacs” was used in the letters of Avitus of Vienne (494/6 – 518), in conciliar legislation, and in penitential and hagiographical compositions as a means of expressing the needs of the ecclesiastical elite, primarily to exclude those who would challenge institutional power. The image that arises from these sources of Bonosiacs, and of heretics more generally, is often helpfully contextualized by examining the political background. In a body of work that reflects a century of theological thought, heresiology was ultimately circumscribed by power dynamics, in which the boundaries of orthodoxy were negotiated with an eye toward the material.