Isabella I of Jerusalem

Isabella I (1172 – 5 April 1205) was the queen of Jerusalem from 1190 to her death in 1205. She was the daughter of King Amalric of Jerusalem and his second wife, the Byzantine princess Maria Comnena. Isabella was a younger half-sister of King Baldwin IV and Queen Sibylla of Jerusalem. Her half-brother married her to Humphrey IV of Toron. Isabella and Humphrey's respective stepfathers, Balian of Ibelin and Raynald of Châtillon, were influential members of the two baronial parties. The couple's marriage was celebrated in Kerak Castle in autumn 1183. Saladin, the Ayyubid sultan of Egypt and Syria, laid siege to the fortress during the wedding, but Baldwin IV forced him to lift the siege.

Baldwin IV suffered from leprosy and made his nephew Baldwin of Montferrat (Sibylla's son) his heir and co-ruler to prevent the boy's stepfather, Guy of Lusignan, from becoming king. The High Court of Jerusalem stipulated that a committee of Western European rulers was entitled to choose between Isabella and Sibylla to succeed Baldwin V if he died before reaching the age of majority. However, Sibylla and Guy were crowned soon after her son died in 1185. Guy's opponents tried to play Isabella and her husband off against him, but Humphrey did homage to the royal couple.

After her half-sister died in 1190, Isabella's mother and stepfather had her marriage to Humphrey annulled so she could marry Conrad of Montferrat. Isabella and Conrad claimed the throne in opposition to the widowed Guy, and they were elected queen and king of Jerusalem in 1192, shortly before Conrad's assassination. Count Henry II of Champagne was hastily elected king and married to Isabella. Her fourth marriage, following Henry's death in 1197, was to King Aimery of Cyprus. Isabella and Aimery were crowned at Acre in 1198. After the couple both died in 1205, Isabella was succeeded by Maria, her eldest daughter with Conrad of Montferrat.