Ablative armor is armor designed to negate damage by itself being damaged or destroyed. The idea is most commonly encountered in science fiction, as this type of armor would be most effective versus electromagnetic energy emissions and particle beams.

Ablative armor would undergo a state change on weapon impact, perhaps vaporising, or disintegrating to a fine powder. This state change should be endothermic, as the effectiveness of ablative armor, like all armor, depends on its ability to absorb incoming weapon energy.

Secondary benefits of ablative armor versus beam weapons would be that outwardly expelled armor debris might serve to disrupt the coherence of incoming beams. This could be enhanced by the incorporation of reflective components to the armor material.

Ablative armor is distinct from the concept of reactive armor, which uses a sandwich layer of explosives to disrupt the thrust of armor piercing munitions , and is actually in common use in modern armored vehicles.