The Order of Knights of the Hospital of Saint John of Jerusalem (Latin: Ordo Fratrum Hospitalis Sancti Ioannis Hierosolymitani; Italian: Cavalieri dell’Ordine dell’Ospedale di San Giovanni di Gerusalemme), also known as the Order of Saint John, Order of Hospitallers, Knights Hospitaller, Knights Hospitalier or Hospitallers, was a medieval and early modern Catholic military order. It was headquartered in the Kingdom of Jerusalem, on the island of Rhodes, in Malta and St Petersburg.
The Hospitallers arose in the early 11th century, at the time of the great monastic reformation, 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 military religious 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 to briefly colonise parts of the Americas: they acquired four Caribbean islands in the mid-17th century, which they turned over to France 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, although ecumenical relations between the descendant chivalric orders are amicable. 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.