William V, Marquess of Montferrat

William V of Montferrat (occ./piem. Guilhem, it. Guglielmo) (c. 1115 – 1191) also known regnally as William III of Montferrat while also referred to as William the Old or William the Elder, in order to distinguish him from his eldest son, William Longsword, was marquess of Montferrat from c. 1136 to his death in 1191. William was the only son of marquess Renier I and his wife Gisela, a daughter of William I, Count of Burgundy and widow of Count Humbert II of Savoy. It seems likely, given that he was still fit enough to participate in battle in 1187, that William was one of his parents' youngest children.

He was described by Acerbo Morena as of medium height and compact build, with a round, somewhat ruddy face and hair so fair as to be almost white. He was eloquent, intelligent and good-humoured, generous but not extravagant. Dynastically, he was extremely well-connected: a nephew of Pope Callixtus II, a half-brother of Amadeus III of Savoy, a brother-in-law of Louis VI of France (through his half-sister Adelasia of Moriana), and cousin of Alfonso VII of Castile.

William married Judith or Ita von Babenberg, daughter of Leopold III of Austria and Agnes of Germany, sometime before March 28, 1133. Judith was probably about 15 at the time. None of their surviving children seem to have been born before 1140 (there may have been older ones who died in infancy), and the youngest son was born in 1162. She died after 1168. They had five sons, four of whom became prominent in the affairs of the Kingdom of Jerusalem and of Byzantium:

• William Longsword, Count of Jaffa and Ascalon, father of Baldwin V of Jerusalem
• Conrad, King of Jerusalem
• Boniface, his successor to Montferrat and founder of the Kingdom of Thessalonica
• Frederick, who entered the Church and became Bishop of Alba (dates uncertain).
• Renier, married into the Byzantine imperial family

and three daughters:

• Agnes, who married Count Guido Guerra III Guidi conte di Modigliana The marriage was annulled on grounds of childlessness before 1180, when Guido remarried, and Agnes entered the convent of Santa Maria di Rocca delle Donne.
• Adelasia or Azalaïs (d. 1232), who married Manfred II, marquess of Saluzzo, c. 1182, and was regent for her grandson Manfred III.
• An unidentified daughter, who married Albert, marquess of Malaspina.

The vida of the troubadour Raimbaut de Vaqueiras claims that there was another daughter, Beatrice, who m. Henry I del Carretto, marquess of Savona, and that she is the Bel Cavalher (Fair Knight) of Vaqueiras's songs. However, the lyrics of Vaqueiras's songs (as opposed to the later vida) describe Beatrice as Boniface's daughter, and thus William's granddaughter.

Otto (Oddone of Montferrat, d. 1251), who became Bishop of Porto, and Cardinal in 1227, has sometimes been identified as a son of William V, and confused with Frederick. However, his dates make it more likely that he was a son of William VI of Montferrat, whether legitimate or not is uncertain.

William and Judith's powerful dynastic connections created difficulties in finding suitable wives for his sons, however: too many potential spouses were related within prohibited degrees. In 1167, he unsuccessfully tried to negotiate marriages for his eldest sons to daughters of Henry II of England - but the girls were very young at the time and were related through Judith's descent from William V of Aquitaine. He then applied for sisters of William I of Scotland, who were not related, but were already married.

William took part in the Second Crusade, alongside his half-brother Amadeus of Savoy (who died during the campaign), his nephew Louis VII of France, his brother-in-law Count Guido of Biandrate, and his wife's German and Austrian relatives.

As supporters of the imperial party (later known as the Ghibellines), he and his sons fought with the Emperor Frederick Barbarossa (Judith's nephew) in his lengthy struggle against the Lombard League. Following Barbarossa's capitulation with the Peace of Venice in 1177, William was left to deal with the rebellious towns in the area alone. Meanwhile, the Byzantine emperor Manuel I Komnenos sought support for his own politics in Italy.

William broke with Barbarossa and formed an alliance with Manuel. His eldest surviving son, Conrad, was taken prisoner by Barbarossa's Chancellor, Archbishop Christian of Mainz, but then captured the chancellor in battle at Camerino. In 1179 Manuel suggested a marriage between his daughter Maria, second in line to the throne, and one of William's sons. As Conrad and Boniface were already married, the youngest son, Renier, was married off to the princess, who was ten years his senior. Renier and Maria were later killed during the usurpation of Andronikos, and the family rebuilt ties with Barbarossa.

In 1183, with the accession of his grandson Baldwin V, a minor, as co-King of Jerusalem, William, then probably in his late sixties, left the government of Montferrat to Conrad and Boniface, and returned to the east. He was granted the castle of St. Elias (present-day Taybeh). He fought in the Battle of Hattin in 1187, where he was captured by Saladin's forces. In the meantime, his second son, Conrad, had arrived at Tyre from Constantinople. Conrad was given the command of the defences. During the siege of Tyre in November that year, he is said to have refused to surrender as much as a stone of its walls to liberate his father, even threatening to shoot him with a crossbow himself when Saladin had him presented as a hostage. Eventually, Saladin withdrew his army from Tyre. In 1188, William was released unharmed at Tortosa, and seems to have ended his days in Tyre, with his son. He probably died in the summer of 1191: Conrad last describes himself as "marchionis Montisferrati filius" in a charter of May that year.

William de Montferrat is an assassination target in the video game Assassin's Creed. In the game, de Montferrat is Liege Lord of Acre under King Richard and is portrayed as middle aged, rather than in his early eighties.