Armor (in British English) or armor (in American English; see spelling differences) is a protective layer that is often used to prevent damage to objects, individuals or vehicles caused by weapons or projectiles in direct contact with them in combat, or by potentially hazardous environments or actions (e.g., bicycles, construction sites, etc.).

Personal armor is used to protect soldiers and war animals. Vehicle armor is used for warships and armored combat vehicles.

The second use of the word armor describes armored forces, armored weapons and their role in combat. With the development of armored warfare, mechanized infantry and their weapons are called "armor".