Isabella I (1172 – 5 April 1205) was Queen regnant of Jerusalem from 1190 to her death. She was the daughter of Amalric I of Jerusalem and his second wife Maria Comnena. Her half-brother, Baldwin IV of Jerusalem, engaged her to Humphrey IV of Toron. Her mother's second husband, Balian of Ibelin, and his stepfather, Raynald of Châtillon, were influential members of the two baronial parties. The marriage of Isabella and Humphrey 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.