Defensive covering for the head, one of the most universal forms of armor. Helmets are usually thought of as military equipment.

Military helmets date from ancient times. Their basic function was to protect the head, face, and sometimes the neck from the cutting blows of swords, spears, arrows, and other weapons. The Assyrians and Persians had helmets of leather and iron, and the Greeks brought helmet making to a pinnacle of craftsmanship with their bronze helmets, some of which covered the entire head, with only a narrow opening in front for vision and breath. The Romans developed several forms of helmets, including the round legionary's helmet and the special gladiator's helmet, with broad brim and pierced visor, giving exceptional protection to head, face, and neck.

In northern and western Europe, early helmets were of leather reinforced with bronze or iron straps and usually took the form of conical or hemispherical skullcaps. Gradually the amount of metal increased until entire helmets were fashioned of iron, still following the same form. About the year 1200 the helm, or heaume, emerged. It was a flat-topped cylinder that was put on over the skullcap just before an engagement; experience soon dictated rounded contours that would cause blows to glance off. At the same time, the skullcap developed into the basinet, with pieces added to protect the neck and with a movable visor for the face. By 1500 several highly sophisticated types of helmets were in use, employing hinges or pivots to permit the piece to be put on over the head and then fitted snugly around head and neck so that it could not be knocked off in combat.

In the 16th and 17th centuries light, open helmets with broad brims became popular. In the 18th and 19th centuries, with the growing effectiveness of firearms and the consequent decline in use of the sword and spear, helmets largely disappeared except for the use of light helmets by cavalry. The steel helmet reappeared, however, as a standard item for infantry in the opening years of World War I because it protected the head against the high-velocity metal fragments of exploding artillery shells. The French first adopted the helmet as standard equipment in late 1914 and were quickly followed by the British, the Germans, and then the rest of Europe. The typical helmet is a hardened-steel shell with an inner liner and weighs about 1 to 4 pounds (0.5 to 1.8 kg).

Conical iron and steel helmets -- developed in medieval Persia, Turkey, and India -- are valued as works of art because of their fine forging and delicate damascening. In Tibet and China, helmets of bronze, leather, and horn have been made for centuries, while Japanese helmets with detachable face guards, finely forged and lacquered, have been recognized as outstanding examples of the armory's craft.