Ablative armor is armor which prevents damage through the process of ablation, the removal of material from the surface of an object by vaporization, chipping, or other erosive processes. In contemporary spacecraft, ablative plating is most frequently seen as an ablative heat shield for a vehicle that must enter atmosphere from orbit, such as on nuclear warheads, or space vehicles like the Mars Pathfinder probe. A large amount of developmental usage was on the early 1960s rocket powered X-15 crewed aircraft traveling at hypersonic speeds in excess of Mach 6.5 (roughly 5,000 mph). The idea is also commonly encountered in science fiction. In recent years, the concept has had widespread usage in robot combat as a method of reducing impact energy transfer to vital components.

Ablative armor is distinct from the concept of reactive armor which is actually in common use in modern armored vehicles.