Gerard (c. 1040 – September 3, 1120), variously surnamed Tum, Tune, Tenque or Thom, was the founder of the Order of the Knights of St. John of Jerusalem, or the Knights Hospitaller.

He was born possibly at Amalfi, or according to other accounts Martigues in Provence, while one authority even names the Chateau d'Avesnes in Hainaut. Either as a soldier or a merchant, he found his way to Jerusalem, where a hospice had for some time existed for the convenience of those who wished to visit the Christian holy places. Of this institution Gerard became guardian or provost at a date not later than 1100, and here he organized that religious order of St John which received papal recognition from Paschal II in 1113, by the bull Geraudo institutori ac praeposito Hirosolimitani Xenodochii. It was renewed and confirmed by Calixtus II shortly before the death of Gerard in 1120.

Raymond du Puy de Provence (1083 - 1160), was a French knight and was Grand Master of the Order of St. John of Jerusalem (Knights Hospitaller) from 1118-1160. He was the son of Hughes Du Puy (1060-?), Seigneur de Pereins, d'Apifer, et de Rochefort, Governor of Acre and a general of Godfrey of Bouillon. He was also a relative of Adhemar of Le Puy, the papal legate during the First Crusade. As the second Grand Master he developed the Knights Hospitaller into strong military power. He accepted the eight- pointed Amalfi cross as an official symbol of the Order, which later became known as the Maltese Cross after the establishment of the Order on Malta. Raymond divided the Order into clerical, military, and serving brothers and established the first significant Hospitaller infirmary near the Church of the Holy Sepulchre in Jerusalem. He was present at the capture of Ascalon in 1153.

Gilbert of Assailly (d.1183) was Grand Master of the Knights Hospitallers from 1162/3 to 1170, when he resigned or was deposed. During his time at the head of the Hospitallers, they purchased the land for Castle Belvoir, at Kawkab al-Hawa, now Beit She'an, and otherwise expanded their fortifications. Gilbert also began regulating the constitution of the order. His is principally remembered for his militant attitude to the invasion of Egypt, proposed by Amalric I of Jerusalem. The 1168 expedition turned out disastrously, and Gilbert's position became untenable.

Jobert of Syria (also rendered Gilbert, Josberto, or Joubert) (d.1177) was the seventh Grand Master of the Knights Hospitaller from 1172 to his death, which is assumed from his disappearance from history to have occurred in 1177. He succeeded Cast de Murols (1170-1172), while Cast's predecessor, Gilbert d'Aissailly, who was still living, had been deposed. The memory of Gilbert must have informed Jobert how not to waste the Order's funds, for he seems to have been a responsible steward of the order's assets. He set aside property for the production of white bread for the poor at the hospital in Jerusalem.

In August 1174, he refused to commit, along with the other Orders, to aiding the Sicilian navy in attacking Egypt with Miles de Plancy, the regent of the Kingdom of Jerusalem. In December, however, he joined the new regent, Raymond III of Tripoli, in a planned attack on Sultan Saladin. He and his forces were with the army which menaced Homs after Saladin had taken it. Battle was not engaged, and the Franks left in exchange for the release of hostages and remission of ransoms.

In 1176, Baldwin IV of Jerusalem confirmed a grant of lands in Egypt to the Order in exchange for assistance from Jobert in the planned campaign there. Though Jobert supported the Egyptian policy, he is last mentioned in January 1177, and his successor, Roger de Moulins, did not agree with the plan and it was abandoned.

Garnier de Nablus was Grand Master of the Knights Hospitaller from 1190 to 1192. He fought at the battle of Arsuf under Richard the Lionheart. Legend has it that when he was pressed by the Muslims during the battle, he rode forward in person and asked Richard to relieve the pressure with a cavalry charge. Richard replied 'Good Master, it is you who must sustain the charge; no man can be everywhere at once'. It is said that when the pressure increased, the Grand Master and one other knight broke ranks and charged the Muslims, joined soon after by the rest of the force. Richard, seeing that his orders were already disobeyed, signalled for a full charge. This caught the enemy at a vulnerable moment, and their ranks were broken. Thus, in some ways de Nablus helped win the battle, though in contravention of Richard's orders.

Pierre Guérin de Montaigu (d. 1230) was a nobleman from Auvergne, who became the 13th Grand Master of the Knights Hospitaller, in 1207-8.

He intervened in Armenia to help the Christian population against Suleiman of Iconium. He helped raise the siege of Acre by the Sultan of Damascus.

He distinguished himself at the capture of Damietta during the Fifth Crusade, and subsequently toured European countries seeking support. On his return to Palestine, he found turmoil; he tried vainly to reconcile the Hospitallers with the Knights Templar.

In 1228 he persuaded the Pope to break the truce holding between Christian and Muslim powers. He refused however to serve in the army commanded by Emperor Frederick II, who was excommunicated.

He died in Palestine.

Guillaume de Villaret (Occitan: Guilhem del Vilaret) (d. 1305), a native of Languedoc-Roussillon was the 24th Grand Master of the Knights Hospitallers, a position he held from 1296 to his death. He was succeeded by his nephew, Foulques de Villaret, whose career he had done much to advance.

In 1300, in response to the urgent remonstrances of the knights, he appeared in Cyprus. His Order participated in an ill-fated expedition with other Cypriots, meaning the Knights Templar, the Teutonic Knights, and the Kingdom of Jerusalem, to launch coastal raids along the Egyptian, Palestine and Syrian coasts in 1300. The Cypriots, under King Henry II, then sent a land-based source to the island of Arwad, in an attempt to retake the coastal city of Tortosa. There had been some attempt to do this in concert with forces from the Mongol Ilkhanate; however the promised Mongol troops did not arrive, the Cypriots eventually had to retreat from Ruad, and the island was re-taken by the Egyptian Mamluks a year later.

Pierre d'Aubusson (1423 - June 30, 1503) was a Grand Master of the order of St. John of Jerusalem (the Knights Hospitaller) and a zealous opponent of the Ottoman Empire.

Pierre probably joined the Knights of St. John in 1444 or 1445 and then left for Rhodes.

Pierre d'Aubusson was elected "Grand Prior" of the "Langue d'Auvergne" in early 1476. In June 1476, he was elected Grand Master of the Order, having been a very close associate of a previous Grand Master, Raymond Zacosta, and responsible for the repair and modernization of the fortifications of the city of Rhodes, the other castles of the Order on the islands of the Dodecanese, and the Château Saint Pierre (formerly Halicarnasse, today Bodrum, Turkey).

Sultan Mehmed II began to threaten Europe. In May 1480 a large Ottoman fleet appeared before Rhodes, carrying an invading army of some 100,000 men under the command of Mesih Pasha (originally a Greek by the name of Michael Palaiologos who had converted to Islam after the conquest of Constantinople by the Turks).

The Knights were reinforced from France by 500 knights aud 2000 soldiers under d'Aubusson's brother Antoine. The siege lasted until August. After three unsuccessful attempts againsts the City, the Turkish force was compelled to withdraw, leaving behind them 9000 dead. The siege, in which d'Aubusson was wounded three times, enhanced his renown throughout Europe.

Sultan Mehmed was furious and would have attacked the island again but for his death in 1481. His succession was disputed between his sons Bayezid and Cem. The latter, after his defeat by Bayezid, sought refuge at Rhodes under a safe-conduct from the Grand Master and the General Convent of the Order.

Rhodes not being considered secure, Cem with his own consent was sent to Bourganeuf in France where he was kept under the guard of Guy de Blanchefort, Pierre d'Aubusson's nephew.

D'Aubusson accepted an annuity of 45,000 ducats from Sultan Bayezid, in return for which he undertook to guard Cem in such a way as to prevent him from appealing to the Christian powers to aid him against his brother.

D'Aubusson's reward was a cardinal's hat (1489) and the power to confer all benefices connected with the Order without the sanction of the papacy. In addition, the Order of St. John received the assets of the Order of the Holy Sepulchre, which was merged into the Order of St. John, and a number of Italian commandries of the Knights of St. Lazarus.

Jean de la Vallette was Grand Master of the Order of the Knights of Saint John of Malta (Hospitallers). He defeated the Turkish invasion of Malta. He then decided to build a new fortified city at the Sciberras Heights to repel any future attack. He laid the first stone of the city, but died before completion. As an act of respect the city was named after him. It is the capital city of Malta still, Valletta.

Fra Pietro del Monte was an Italian who succeeded La Vallette as Grand Master of the Knights Hospitaller at Malta. He continued the construction of Valletta. One of his contributions to the military history of Malta was the building of Del Monte Gate which was eventually demolished and replaced by the Victoria Gate.

Jean de la Cassière was the Grand Master of the Knights of Malta in the 16th Century, who commissioned the building of the Conventual Church of the Order (St John's Co-Cathedral) in Valetta, Malta. He is buried in the Crypt of St. John.