Known as the Order of Saint John, Order of Hospitallers, Knights Hospitaller, or Hospitallers, was the name of the medieval Catholic military order that preceded the contemporary Sovereign Military Order of Malta, which remains a sovereign subject of international law. It was headquartered variously in the Kingdom of Jerusalem, Rhodes and Malta, until it became known by its current name.
The Hospitallers probably arose as a group of individuals associated with an Amalfitan hospital in the Muristan district of Jerusalem, dedicated to John the Baptist and founded around 1023 by Gerard Thom to provide care for sick, poor or injured pilgrims coming to the Holy Land. Some scholars, however, consider that the Amalfitan order and hospital were different from Gerard Thom's order and its hospital.After the conquest of Jerusalem in 1099 during the First Crusade, the organisation became a religious and military order under its own Papal charter, charged with the care and defence of the Holy Land. Following the conquest of the Holy Land by Islamic forces, the knights operated from Rhodes, over which they were sovereign, and later from Malta, where they administered a vassal state under the Spanish viceroy of Sicily. The Hospitallers were the smallest group ever to colonise parts of the Americas; at one point in the mid-17th century, they acquired four Caribbean islands, which they turned over to the French and Dutch in the 1660s.
The knights were weakened in the Protestant Reformation, when rich commanderies of the order in northern Germany and the Netherlands became Protestant and largely separated from the Roman Catholic main stem, remaining separate to this day. The order was disestablished in England, Denmark, Sweden and elsewhere in northern Europe,and it was further damaged by Napoleon's capture of Malta in 1798, following which it became dispersed throughout Europe and Russia. It regained strength during the early 19th century as it redirected itself toward religious and humanitarian causes. In 1834, the order, by this time known as the Sovereign Military Order of Malta, acquired new headquarters in Rome, where it has since been based.