A military order (Latin: militaris ordinis) is a Christian religious society of knights. The original military orders were the Knights Templar, the Knights Hospitaller and the Teutonic Knights. They arose in the Middle Ages in association with the Crusades, their members being dedicated to the protection of pilgrims and the defence of the Crusader states. They are the predecessors of the secular chivalric orders.
Most members of military orders were laymen who took religious vows, such as of poverty, chastity, and obedience, according to monastic ideals. The orders owned houses called commanderies all across Europe and had a hierarchical structure of leadership with the grand master at the top.
The Knights Templar, the largest and most influential of the military orders, was suppressed in the early fourteenth century; only a handful of orders were established and recognized afterwards. However, some persisted longer in their original functions, such as the Sovereign Military Order of Malta and the Order of Saint John, the respective Catholic and Reformed successors of the Knights Hospitaller. Those military orders that survive today have evolved into purely honorific or ceremonial orders or else into charitable foundations.