Iconoclasm (from Greek: εἰκών, eikṓn, 'figure, icon' + κλάω, kláō, 'to break') 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."

Conversely, one who reveres or venerates religious images is called (by iconoclasts) an iconolater; in a Byzantine context, such a person is called an iconodule or iconophile. Iconoclasm does not generally encompass the destruction of the images of a specific ruler after his or her death or overthrow, a practice better known as damnatio memoriae.

While iconoclasm may be carried out by adherents of a different religion, it is more commonly the result of sectarian disputes between factions of the same religion. The term originates from the Byzantine Iconoclasm, the struggles between proponents and opponents of religious icons in the Byzantine Empire from 726 to 842 AD. Degrees of iconoclasm vary greatly among religions and their branches, but are strongest in religions which oppose idolatry, including the Abrahamic religions. Outside of the religious context, iconoclasm can refer to movements for widespread destruction in symbols of an ideology or cause, such as the destruction of monarchist symbols during the French Revolution.