Natural armor is a rule where creatures attribute part of their armor class to their innate tough hide, scales, or skin. It is generally a trait of monsters, rather than player characters.
Publication history[]
AD&D 1st edition[]
Natural armor was first mentioned in Natural Armor for Monsters in Monsters, Monsters, Dragon #17 (Aug 1978), p.33.
D&D 3rd edition[]
Natural armor is a core mechanic in D&D 3rd edition. Natural armor is ignored when rolling to hit touch AC, such as a spell attack. A character with natural armor can benefit from both natural armor and worn armor at the same time.
D&D 5rd edition[]
A character can only benefit from either natural armor or worn armor, but not both at once. This prevents players from combining both to attain a very high armor class.