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. Over time, the word, usually in the adjectival form, has also come to refer to aggressive statements or actions against any well-established status quo. It is a frequent component of major political or religious changes. The term does not generally encompass the specific destruction of images of a ruler after his death or overthrow (damnatio memoriae).

People who engage in or support iconoclasm are called iconoclasts, a term that has come to be applied figuratively 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 may be carried out by people of a different religion, but is often the result of sectarian disputes between factions of the same religion. Within Christianity, iconoclasm has generally been motivated by those who adopt a literal interpretation of the Ten Commandments, which forbid the making and worshipping of "graven images or any likeness of anything".The Church Fathers identified Jews, fundamental iconoclasts, with heresy and saw deviations from orthodox Christianity and opposition to the veneration of images as heresies that were essentially "Jewish in spirit". The degree of iconoclasm among Christian branches greatly varies. Islam, in general, tends to be more iconoclastic than Christianity, with Sunni Islam being more iconoclastic than Shia Islam.