Isabella I (Old French: Ysabel; c. 1172 – 1205) was the queen of Jerusalem who reigned from the early 1190s to her death. She received the homage of her vassals as the rightful heir to the throne after the death of her half-sister Queen Sibylla in 1190, but Sibylla's widower, Guy of Lusignan, held onto the kingdom until 1192. Isabella became queen upon her coronation in 1198. Having little political ambition, she passed the government on to three successive husbands, Conrad of Montferrat, Henry II of Champagne, and Aimery of Lusignan, all of whom included her in the issuing of their charters. Isabella's co-reign with Aimery saw the compilation of the Livre au roi, a law treatise establishing the rights and obligations of queens regnant of Jerusalem.
Isabella was the daughter of King Amalric and his second wife, Maria Komnene. After Amalric's death in 1174, Queen Maria married Balian of Ibelin. The marriage of Amalric's elder daughter, Sibylla, to the controversial Guy of Lusignan divided the nobility in two camps, with Isabella's stepfamily opposing Guy. Isabella's half-brother King Baldwin IV arranged for her to marry the lord Humphrey IV of Toron, whose family supported Guy and opposed the Ibelins. Baldwin IV suffered from leprosy and could not sire an heir; he named Sibylla's son, Baldwin V, as his successor. The High Court stipulated that a committee of Western European rulers was entitled to decide whether Sibylla or Isabella should inherit the throne if Baldwin V died. When Baldwin V died in 1186, Sibylla seized the throne before the committee could choose. Guy's opponents wished to install Isabella as anti-queen, but her husband, Humphrey, recognized Sibylla and Guy as rulers.
In 1190, after Queen Sibylla died in the midst of the Third Crusade, Isabella's mother and stepfather forced her to leave Humphrey so that she could marry Marquis Conrad of Montferrat and claim the throne against Guy. The crusading Kings Richard I of England and Philip II of France arbitrated and declared that Guy should retain the kingship for his lifetime and be succeeded by Isabella and Conrad. Conrad was elected king when Guy left the kingdom in 1192, but was assassinated shortly after. The nobles selected Count Henry II of Champagne to succeed Conrad, and Isabella hastily married him. Her fourth marriage, celebrated shortly after Henry's accidental death in 1197, was to Guy's brother, King Aimery of Cyprus. Aimery died in 1205 and Isabella herself died a few months later, at which time her kingdom passed to Maria of Montferrat, the eldest of her five surviving daughters.
Born between November 1171 and September 1172, Isabella was the daughter of King Amalric and his second wife, the Byzantine-born Maria Komnene. Her parents' other child, a daughter who was probably older, died in infancy. Isabella had two older half-siblings, Sibylla and Baldwin, born from Amalric's first, annulled marriage with Agnes of Courtenay. Amalric died of dysentery on 11 July 1174. Noblemen and clergy convened to discuss the succession to the Kingdom of Jerusalem, a crusader state surrounded by hostile Muslim powers. There were signs that Baldwin, the king's only son, might develop leprosy, but the claims of Sibylla, an unmarried girl, and Isabella, aged only two, were not viable. The assembly thus settled on Baldwin IV. Maria then retired with Isabella to the town of Nablus, which she had received from Amalric as her dower.
Soon after his accession, it became obvious that Baldwin suffered from lepromatous leprosy. To secure the succession to the ailing king, his sister, Sibylla, was given in marriage to William of Montferrat in November 1176, but William died in June 1177. Sibylla's cousin Count Philip I of Flanders arrived in the kingdom in August and proposed that Sibylla and Isabella should marry the brothers Robert and William of Bethune, respectively. The High Court of Jerusalem refused both proposals.
Isabella's mother, Queen Maria, married Balian of Ibelin in late 1177. His brother Baldwin of Ibelin wanted to marry Sibylla, but King Baldwin chose another candidate, Guy of Lusignan. Sibylla and Guy's marriage in 1180 caused a rift in the kingdom. Guy was supported by his mother-in-law, Agnes; her brother, Joscelin; and Raynald of Châtillon, the lord of Transjordan. Their opponents included Isabella's mother and stepfather and Count Raymond III of Tripoli, who was a first cousin of King Amalric.
King Baldwin solemnly betrothed the eight-year-old Isabella to Raynald of Châtillon's fifteen-year-old stepson, Humphrey IV of Toron, in Jerusalem in October 1180. Archbishop William of Tyre drew up the marriage contract, according to which Humphrey ceded his fiefs of Toron, Chastelneuf, and the right to Banias to Baldwin. Still, the couple were not married immediately because Isabella had not yet reached the canonical age of twelve. Baldwin probably wished that the legality of the marriage be beyond doubt. The match was likely the idea of the king's mother, Agnes, who received Humphrey's lands in return. The historian Steven Runciman interpreted this betrothal as an attempt to heal the division between the two factions, while his colleague Bernard Hamilton argues that–on the contrary–it was meant to prevent the Ibelins from choosing Isabella's husband if Baldwin should die. After the betrothal to Humphrey, Isabella was sent to Kerak Castle to live with Humphrey's mother, Stephanie of Milly. Stephanie forbade her from visiting her mother in Nablus, effectively isolating her from any potential conspirators who might attempt to place her on the throne.
The religious marriage of Isabella and Humphrey was scheduled for late 1183, and professional entertainers flocked to Kerak Castle from around the region. Saladin, the Ayyubid sultan of Egypt and Syria, probably heard about the festivities and decided to try to take valuable hostages. He set out from Damascus on 22 October and laid siege to Kerak. According to Ernoul's chronicle, Stephanie of Milly sent feast dishes to Saladin, who forbade his engineers from bombarding the tower in which Humphrey and Isabella were lodged. Ernoul was likely informed by Isabella's mother, Queen Maria.
Baldwin IV's relationship with Guy of Lusignan had worsened by then, and Guy had shown that he was unable to command the royal army. When the news of Isabella's predicament at Kerak reached Jerusalem, the king and his council decided that Guy was not fit to be king. Isabella and Humphrey's claim could not be entertained because they were in danger of becoming captives. Baldwin IV thus had Sibylla's son by her first marriage, Baldwin V, crowned as co-king on 20 November 1183. The ailing king may have named his nephew as co-ruler to avoid a succession dispute between his sisters' supporters. Guy's principal allies, Joscelin of Courtenay and Raynald of Châtillon, were not present at Baldwin V's coronation; Raynald was attending the wedding at Kerak, and Joscelin probably was too. After Baldwin IV led a relief army to Kerak, Saladin lifted the siege and retreated without a fight on 4 December.
Baldwin IV died in early 1185, having appointed Raymond of Tripoli regent for Baldwin V. Raymond accepted the regency on the condition, approved by the High Court, that a committee consisting of the pope, the Holy Roman emperor and the kings of France and England would choose between Sibylla and Isabella if Baldwin V died before reaching the age of majority.
In mid-1186, Baldwin V died too. Sibylla's uncle, Joscelin of Courtenay, persuaded Raymond of Tripoli and his allies to leave Jerusalem, and urged her supporters (including Raynald of Châtillon) to assemble in the town. Ignoring the 1185 ruling of the High Court, the noblemen and prelates who came to Jerusalem declared Sibylla the lawful heir to the throne. Raymond summoned the nobles to Nablus; those who attended his council probably included Isabella, her husband, and her stepfamily. They argued that Sibylla's legitimacy was dubious because her parents' marriage had been annulled and emphasized that Isabella was born after their father's coronation. The nobles at Nablus sent envoys to Jerusalem to forbid Sibylla's coronation, but it went ahead anyway; Sibylla then crowned Guy.