Sibylla was born circa 1160 as the daughter of Agnes of Courtenay and Amalric I of Jerusalem. She was raised by her great-aunt Ivota of Bethany, who was the sister of Queen Melisende of Jerusalem. By 1174 she was the subject of marriage negotiations. Sibylla had two siblings, a younger brother Baldwin who was sickly and Isabella. Because of her brother’s health, her marriage was of great concern. She was engaged to Stephen I of Sancerre, but he changed his mind for unknown reasons.
Her brother became King upon their father’s death in 1174. He arranged her marriage to William Longsword of Montferrat in 1176. She was created Countess of Jaffa and Ascalon, a title previously held by her mother. William died in June 1177, leaving behind a pregnant Sibylla. She gave birth to her son Baldwin in August of 1177. She remained a prize on the marriage market but did not remarry again until 1180. In April of 1180, she married Guy of Lusignan, and they had two daughters, who did not live long, named Alice and Maria.
Her brother had much trust in Guy and even appointed him regent when he was incapacitated, though this did not last long as he did not approve of Guy’s behaviour. In response he had Sibylla’s son Baldwin crowned co-King as Baldwin V, passing her over in the succession. He also attempted to annul their marriage.
Her brother died in 1185, leaving Sibylla’s son as sole King at the age of 8. However, his reign wouldn’t last long as his health was frail. The boy king died in 1186 and was succeeded by his own mother, despite claims from her sister Isabella that she was removed from the succession. Her reign was marred by war. Her husband was captured during the Battle of Hattin in 1187, and later that year the Holy City was under siege. Jerusalem capitulated on 2 October, though she was allowed to escape with her daughters. Guy was eventually released in 1188, and together they marched on Tyre in 118, the only city in the Kingdom that had not fallen. The city was held by Conrad of Montferrat, the brother of Sibylla’s first husband, William. However, he refused to let them enter, and they spent a month outside the city walls. Guy then intended to make Acre the seat of the Kingdom, and he besieged the city for two years. Tragedy struck in July 1190 in the military camp at Acre. Sibylla died just days after both her daughters in an epidemic that swept through the camp.
She was succeeded by her sister Isabella.