Peter of Bruys was a medieval French religious teacher. He was called a heresiarch by the Roman Catholic Church because he opposed infant baptism, the erecting of churches and the veneration of crosses, the doctrine of transubstantiation and prayers for the dead. An angry Roman Catholic mob murdered him in or around 1131.

Iconoclasm is the social belief in the importance of the destruction of icons and other images or monuments, most frequently for religious or political reasons. People who engage in or support iconoclasm are called iconoclasts, a term that has come to be figuratively applied to any individual who challenges "cherished beliefs or venerated institutions on the grounds that they are erroneous or pernicious."