| Isabella I | |
|---|---|
 Marriage of Isabella I (on the right) and Conrad of Montferrat | |
| Queen of Jerusalem | |
| Reign | 1190/1192 – 5 April 1205 |
| Coronation | January 1198 at Acre |
| Predecessor | Sibylla and Guy |
| Successor | Maria |
| Co-rulers | |
| Born | 1172 Nablus, Kingdom of Jerusalem |
| Died | 5 April 1205 (aged 32–33) Acre, Kingdom of Jerusalem |
| Spouses | |
| Issue more... | |
| House | Anjou |
| Father | Amalric I of Jerusalem |
| Mother | Maria Comnena |
| Religion | Roman Catholicism |
Isabella I (1172 – 5 April 1205) was reigning Queen of Jerusalem from 1190 to her death in 1205. She was the daughter of Amalric I of Jerusalem and his second wife Maria Comnena, a Byzantine princess. 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.
Baldwin IV, who suffered from lepromatous leprosy, had made his nephew (the only son of his sister, Sibylla by her first husband), Baldwin V, his heir and co-ruler, to prevent Sibylla's second husband, Guy of Lusignan, from mounting the throne. The High Court of Jerusalem stipulated that a committee of Western European rulers was entitled to choose between Sibylla and Isabella to succeed Baldwin V if he died before reaching the age of majority, but Sibylla and Guy of Lusignan were crowned soon after Baldwin V died in 1185. Guy's opponents tried to play Isabella and her husband off against him, but Humphrey did homage to the royal couple.