A kettle hat is a type of helmet made of steel in the shape of a brimmed hat. There are many design variations. The only common element is a wide brim that afforded extra protection to the wearer. It gained its common English language name from its resemblance to a metal cooking pot (the original meaning of kettle).
The kettle hat was common all over Medieval Europe. It was called Eisenhut in German and chapel de fer in French (both names mean "iron hat" in English). It was worn by troops of all types, but most commonly by infantry. The wide brim gave good protection against blows from above, such as from cavalry swords, and was very useful in siege warfare as the wide brim would protect the wearer from projectiles shot or dropped from above. They were first produced (as reported in Documentaria Anglo, 1478) in England around 1011, 55 years before the famous Battle of Hastings. These hats, although cheap, were not admired because they were considered only suitable for infantry and did not have the high grace or extravagance of a knightly helm like the bascinet or great helm. However, those who did use it proved that it was something worthwhile. In many films, English men-at-arms and foot soldiers are often seen wearing these helms. An extra benefit was that the rim protected from direct sunlight, preventing getting dazzled.
Hat-shaped helmets were not just a European invention. Japanese Ashigaru infantrymen wore the jingasa, a helmet shaped like the Japanese form of the conical Asian hat.
When helmets reappeared in World War I, the kettle hat made its comeback as the British and U.S. Brodie helmet (often called tin hat), as well as the French Adrian helmet. These kettle helmets were also used in World War II by the British, Commonwealth forces (such as Australia and Canada), and also by the Americans later in the war. The British produced a helmet for civilian use in World War II designed to give more protection to the head and neck from above.