The Order of Knights of the Hospital of Saint John of Jerusalem, commonly known as the Knights Hospitaller (), is a Catholic military order. It was founded in the crusader Kingdom of Jerusalem in the 12th century and had its headquarters there, in Jerusalem and Acre, until 1291, thereafter being based in Kolossi Castle in Cyprus (1302–1310), the island of Rhodes (1310–1522), Malta (1530–1798), and Saint Petersburg (1799–1801).
The Hospitallers arose in the early 12th century at the height of the Cluniac movement, a reformist movement within the Benedictine monastic order that sought to strengthen religious devotion and charity for the poor. Earlier in the 11th century, merchants from Amalfi founded a hospital in Jerusalem dedicated to John the Baptist where Benedictine monks cared for sick, poor, or injured Christian pilgrims to the Holy Land. Blessed Gerard, a lay brother of the Benedictine order, became its head when it was established. After the Christian conquest of Jerusalem in 1099 during the First Crusade, the Hospitallers rose in prominence and were recognized as a distinct order by Pope Paschal II in 1113.
The Order of Saint John was militarized in the 1120s and 1130s, hiring knights that later became Hospitallers. The organization became a military religious order under its own papal charter, charged with the care and defence of the Holy Land, and fought in the Crusades until the Siege of Acre in 1291. Following the reconquest 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 also controlled the North African city of Tripoli for two decades in the 16th century, and they were one of the smallest groups to have colonized parts of the Americas, briefly acquiring four Caribbean islands in the mid-17th century, which they turned over to France in the 1660s.
The knights became divided during the Protestant Reformation, when rich commanderies of the order in northern Germany and the Netherlands became Protestant and largely separated from the Catholic main stem, remaining separate to this day; modern ecumenical relations between the descendant chivalric orders are amicable. The order was suppressed in England, Denmark, and other parts of northern Europe, and was further damaged by the French occupation of Malta in 1798, after which it dispersed throughout Europe.
Today, five organizations continue the traditions of the Knights Hospitaller and have mutually recognized each other: the Sovereign Military Order of Malta, the Most Venerable Order of the Hospital of Saint John, the Bailiwick of Brandenburg of the Chivalric Order of Saint John, the Order of Saint John in the Netherlands, and the Order of Saint John in Sweden.
In 603, Pope Gregory I commissioned the Ravennate Abbot Probus, who was previously Gregory's emissary at the Lombard court, to build a hospital in Jerusalem to treat and care for Christian pilgrims to the Holy Land. In 800, Emperor Charlemagne enlarged Probus's hospital and added a library to it. About 200 years later, in 1009, the Fatimid caliph al-Hakim bi-Amr Allah destroyed the hospital and three thousand other buildings in Jerusalem.
Merchants from Amalfi in southern Italy were given permission by the Egyptian Fatimid Caliph al-Mustansir Billah (r. 1036–1094) to build a monastery in Jerusalem, near the Church of the Holy Sepulchre. The monastery, known as the abbey of St Mary of the Latins (to distinguish them from local Syriac Orthodox Church hierarchy), was served by the Order of Saint Benedict and took in Christian pilgrims travelling to visit the Christian holy sites. The increase in the number of pilgrims led the Benedictine monks to establish two hospitals in the late 1060s, one for men and one for women, with the former known as the Hospital of St John. They did this with the support of a wealthy Amalfian named Mauro of Pantaleone. In the early 1070s the hospital was visited by Archbishop John of Amalfi during his pilgrimage. In later centuries, to help raise money in Europe, the Order of St John made claims that the hospital had been founded more than a century before Christ by the high priest Menelaus and the Greek King Antiochus of Jerusalem, with financing from Judas Maccabeus, and that it was first headed by Saint Stephen and had been visited by Christ and the Apostles. A historian of the Order in the 13th century wrote that this version was not true. In any case, the Hospitallers rose to fame and prestige in a short amount of time.
By the time of the success of the First Crusade in 1099, the Hospital of St John was already well known among pilgrims and was regarded as a separate organization from the monastery of St Mary. The monastic brothers at the hospital saw it as their duty to provide the best possible treatment to the poor. They were given an endowment by Godfrey of Bouillon, the leader of the First Crusade, before he died in 1100. The Latin Patriarch of Jerusalem, Ghibbelin of Arles, formally recognized it as a separate entity from the monastery when he reformed the Catholic hierarchy in Palestine, and a step towards this was taken by Pope Paschal II when he recognized the abbey of St Mary as a church of the Holy See, placing it under his protection and exempting it from paying tithes on its land, on 19 June 1112. The monastic Hospitaller Order was formally created when the Pope issued the papal bull Pie postulatio voluntatis on 15 February 1113 to the head of the Hospital of St John, Blessed Gerardo Sasso. The Pope subordinated the hospital to his own authority and exempted it from paying tithes on the lands it owned, and gave the right to its professed brothers to elect their master. He also placed several other hospitals and hospices in southern Italy under the governance of the Hospital of St John in Jerusalem, as they were located at port cities from which pilgrims traveled to the Holy Land.
Gerard acquired territory and revenues for his order throughout the Kingdom of Jerusalem and beyond. Under his successor, Raymond du Puy, the original hospice was expanded to an infirmary and by then was subordinated to the Latin Patriarch of Jerusalem at the Church of the Holy Sepulchre. Around this time the Hospital of St John became connected with that Church, and documents often referred to "the Holy Sepulchre and the Hospital of St John of Jerusalem." Initially, the Hospitallers cared for pilgrims as well as others (including Muslims and Jews) in Jerusalem, but the order soon extended to provide pilgrims with an armed escort before eventually becoming a significant military force. Thus, the Order of St. John imperceptibly became militaristic without losing its charitable character.
It is possible that the Hospital of St John hired knights or foot soldiers after the First Crusade to provide security, before it formally established its own military organization. Knights in western Europe left their horses and weapons to the Hospitallers in their wills in the 1120s, and, in the early 1140s, Pope Innocent II mentioned that the Hospitallers had "servants" to protect pilgrims. An account from a Hospitaller priest in 16th century stated that, as the Order of St John became wealthier, it hired knights to defend its hospitals and pilgrims, and these knights eventually became Hospitallers themselves. It is known that secular knights and soldiers were hired by institutions in Jerusalem to provide protection after 1099, including churches, and some of them later joined military orders. The Order of Knights Templar was founded around 1119-1120 and it is likely that the Hospitallers were inspired by them to have their own knights. A charter made for a gift to the Hospital of St John in a Christian army on 17 January 1126 recorded that a brother from the Order was present as a witness and that he held a military title.
Raymond du Puy, who succeeded Gerard as master of the hospital in 1120, is credited with establishing the military element of the Order. Raymond decided some time before 1136 that Hospitallers could fight to defend the kingdom or to besiege a pagan city. The Knights Hospitaller, like the other military orders, organized its fighting members into the ranks of knight and sergeant. In 1130, Pope Innocent II gave the order its coat of arms, a plain silver cross in a field of red, to differentiate them from the Templars. The other symbol of the Hospitallers, the "eight-pointed cross", is said to have originated in the Byzantine Empire before reaching the Duchy of Amalfi in Italy, and it was later used in Jerusalem by the monks that founded the Hospital of St John. After the Hospitallers moved to Malta, it became known as the Maltese cross.