William VI or Guillem VI (died 1161) was the eldest son of William V and his wife Ermessende, daughter of Count .Archibald Ross Lewis, "The Guillems of Montpellier: A Sociological Appraisal", Viator, 2 (1971): 159–69. William succeeded his father in the lordship of Montpellier in 1121, while still a minor, under his mother's guardianship. He suppressed a revolt of the bourgeoisie in 1143 and participated in several military campaigns of the Reconquista in Spain (1134, 1146–47). He also increased the public character of the lordship in Montpellier and supported the growth of its trade.Archibald Ross Lewis, "Seigneurial Administration in Twelfth-Century Montpellier", Speculum, 22/4 (1947): 562–77.Archibald Ross Lewis, "The Development of Town Government in Twelfth-Century Montpellier", Speculum, 22/1 (1947): 51–67.

Power sharing At the beginning of William's reign, secular authority in Montpellier was shared between the Guillem dynasty, the hereditary viguiers of the town, and the Bishop of Montpellier.Lewis, "Seigneurial Administration", 567–68. In 1139 William confirmed the vicarage to the heirs of the old viguier Bernard Guillem, and the surviving document shows that the viguiers power has increased since 1103 and was probably at its height. William did secure the reaffirmation of his seigneurial rights at Castelnau (1132, 1138) and Lattes (1140). In 1139 William possessed several censives in the suburb of Villa Nova. A cens (plural censives) was a right to tax land, although earlier it had probably been a right to tax persons. By the twelfth-century it could be applied to the lands owing taxes.Lewis, "Seigneurial Administration", 563.

In 1140 a dispute arose between William VI and the bishop over jurisdiction in Montpellieret. The bishop alleged that William was extending the walls and fortifications of the town to encompass some of the episcopal section of Montpellieret and was forcing vassals of the church of Montpellier to contribute to the local defence fund: "William had built a fortification [vallam] to wall his city in the tenancy of the bishop [and had made] the men of Montpellier, and other men of [the cathedral of] the Blessed Peter, [contribute to] the collection of the commune [communitas] of Montpellier."Lewis, "Town Government", 61: vallam ad muniendam villam suam in honore episcopi Guillelmus erigi fecit ... homines Montispessulani, et alios homines Beati Petri ... collationem communitatis Montispessulani. This may show that control of the walls and fortifications was already in the hands of the bourgeoisie, as it certainly was by 1196. It is probable that William was the first lord of Montpellier to oversee the extension of the walls to include territory judicially under the control of all three leading figures in the town.Lewis, "Town Government", 56 n.19.

William's feudal rights included the fealty and homage of several castellanies in the region around Montpellier. He procured general oaths of loyalty from the castellans of these in 1130 and again in 1147. He purchased the castle of Pouget in 1129, and bestowed it on his brother, William of Aumelas, and purchased that of Santeragues in 1147–48.Lewis, "The Guillems of Montpellier", 168. Among the castles which William controlled (some more than others) were Montferrier, Pignan, Coronsec, Frontignan, Valmale and Saint-Pons-de-Mauchiens.

Town administration William inherited the services of two scribes who had worked for his father since at least 1103. One named William, who described himself as a "scribe of Lord William of Montpellier" (scriba domini Guillelmi Montispessulani), operated as late as 1139. Another, Girbertus, officially became scribe in 1113 and continued to serve down to 1125.Lewis, "Seigneurial Administration", 571. William VI also hired his own scribe, Petrus Angelus, between the years 1128 and 1136. Early in William's reign documents start to sharply distinguish knights and other noblemen from burgesses in the witness lists, either by surnames or by title of occupation.Lewis, "Town Government", 57 n.35. In 1139 William instituted an administrative change: he began using a notary (notarius) named Durantus instead of a mere scribe (scriba).He signed documents both as Durantus, Guillelmi, domini Montispessulani, notarius, indicating that his status or occupation was that of notary, and notarius domini Montispessulani, indicating that he held an office from the lord of the town. He served for the remainder of William's reign.

In 1146, William, in preparation for his journey into Spain, handed the government of the town over to his mother, stipulating that should she die it would pass to three burgesses, Olricus Adalguerius, Guillelmus Letericus and Atbrandus, to govern "with the counsel of the other witnesses of this testament."Lewis, "Town Government", 59: cum consilio aliorum testium hujus testimenti. These three burgesses reappear as witnesses to William's last will, indicating their closeness to the ruling clan.Lewis, "Town Government", 60. In 1149 William purchased the jus naufragii (the right to salvage shipwrecks) from the Count of Melgueil for 3,000 sous melgoriens.Lewis, "Seigneurial Administration", 576 n.100. The sou minted at Melgueil was the standard currency of the region, and William was vigilant to insist that the counts of Melgueil not debase it, to detriment of Montpellier's commerce. In 1128, in concluding a war with his son-in-law, Count Bernard IV of Melgueil, William extorted a promise that the coinage would not be debased. William himself controlled the mint, however, and in 1130 he had to agree not issue any coinage on his own authority, but only with the approval of the count.Lewis, "The Guillems of Montpellier", 161–62. These agreements were confirmed in 1132, 1135 and 1145–46.

Revolt of 1141–43 In 1141–42 the viguier Aimon, at the head of the bourgeoisie, led a revolt against William and expelled him from the town. Alfonso Jordan, the Count of Toulouse, "attempted to fish in troubled waters", receiving a strong rebuke from Pope Anacletus II, with whom William VI had a close relationship bordering on an outright alliance. Despite papal support for William, the bishop refused to intervene against the viguier, but with Genoese and Aragonese backing he succeeded in taking back the town after a lengthy siege in 1143, to which Genoa contributed four galleys.Lewis, "Seigneurial Administration", 568 n.39. The papal injunctions were copied into the Guillems' cartulary, the Liber instrumentorum memorialium. The burgesses of Montpellier were scorned as "those so-called consuls" (illi qui ipsius loci consules appelantur). The Chronique Romane highlights the role of Raymond Berengar IV of Barcelona and the siege-induced famine in the surrender of the town:Lewis, "Seigneurial Administration", 568 n.39.

In the year one thousand, one hundred and forty-one, the men of Montpellier ejected lord William of Montpellier from the city, and the lord went to Lattes, and the battle endured two years. The count of Barcelona returned to him [William] the city through a siege. And at that time ten beans were worth one denarius. (En lan de M et C et XLI, giteron los homes de Montpellier en Guillem de Montpellier de la vila, et anet sen a Latas, e duret la batalla II ans: el coms de Barsalona rendet li la villa per assetge: et adones valian X favas 1 d.)

Immediately William set about to destroy the power of the viguier. He razed their castle within the town walls and revoked their judicial privileges and their separate court.Lewis, "Seigneurial Administration", 568 n.41. When the vicarage was divided between Gaucelm de Claret and his nephews in 1150, there is no reference to any judicial privileges or prerogatives like those exercised in 1139 in the surviving document, but there is a reference to "the place where the castle of the vicarage used to stand" (locale ubi fuit castrum vegairale). With Aragonese assistance he initiated new construction on his family's castle in the north of the town. This phase of improvement was not ended until 1152.Lewis, "Seigneurial Administration", 568 n.42. The Chronique Romane says that "the count of Barcelona built the tower of Montpellier" (el coms de Barsalone basti la torre de Montpellier). These moves, and probable the conciliation of the disaffected bourgeoisie, were successful in removing the hereditary viguiers, the Aimons, from a place of influence.

In the aftermath, the process by which the lords of Montpellier "took on a public character, become something more than mere feudal lords," was accelerated. A letter to his Genoese allies dated 1143 begins "William of Montpellier and his burgesses".Lewis, "Seigneurial Administration", 576 n.99: Guillelmus de Montepessulano et burgenses ejus. The coinciding interests of the merchant class and their feudal lords, whose revenues increasingly depended on taxes on commerce, sped up the process by which the lords became representative of the town.Lewis, "Seigneurial Administration", 574–75.

Reconquista In 1134 William VI was with King Alfonso VII of León and Castile when he besieged and took Zaragoza.Jerónimo Zurita, Anales de la Corona de Aragón, II, 32. There he paid homage to and became a vassal of Alfonso.Simon Barton, "Two Catalan Magnates in the Courts of the Kings of León-Castile: The Careers of Ponce de Cabrera and Ponce de Minerva Re-Examined", Journal of Medieval History, 18 (1992), 240, who calls William "Count Guillem of Montpellier". The submission of García Ramírez, the king of Navarre, as well as "many other nobles from Gascony and France had become his vassals" was the justification for Alfonso's coronation as Emperor of Spain in 1135.These others included the Muslim ruler Sayf al-Dawla and the counts of Barcelona and Toulouse, Raymond Berengar IV and Alfonso Jordan, respectively. Among the vassals from Languedoc only William of Montpellier is singled out by name in the Chronica Adefonsi imperatoris, the contemporary account of Alfonso's reign:

All of the nobles from Gascony and from the area up to the Rhone River, including William of Montpellier, came to Alfonso in a spirit of mutual accord. They received silver, gold, horses and many different precious gifts from him. They all became his vassals, and they were obedient to him in all things. . . He presented them with arms and other items. Hence the boundaries of the kingdom of Alfonso, ruler of León, extended from the shores of the Atlantic Ocean, near where the city of our holy patron Santiago is located, all the way to the Rhone River.G. E. Lipskey, The Chronicle of Alfonso the Emperor, PhD thesis (Northwestern University, 1972), I, §68, p. 87, hereafter cited as Chronica. Lipskey's note combines the careers of William V and William VI.