Boniface I, usually known as Boniface of Montferrat (; , Vonifatios Momferratikos) (c. 1150 – 4 September 1207), was the ninth Marquis of Montferrat (from 1192), a leader of the Fourth Crusade (1201–04) and the king of Thessalonica (from 1205). Early life Boniface was the third son of William V of Montferrat and Judith of Babenberg, born after his father's return from the Second Crusade. He was a younger brother of William "Longsword", Count of Jaffa and Ascalon, and of Conrad I of Jerusalem. His youthful exploits in the late 1170s are recalled in the famous "epic letter", Valen marques, senher de Monferrat, by his good friend and court troubadour, Raimbaut de Vaqueiras. These included the rescue of the heiress Jacopina of Ventimiglia from her uncle Count Otto, who was intending to deprive her of her inheritance and send her to Sardinia. Boniface arranged a marriage for her. When Albert of Malaspina (husband of one of Boniface's sisters) abducted Saldina de Mar, a daughter of a prominent Genoese family, Boniface rescued her and restored her to her lover, Ponset d'Aguilar. Like the rest of the family, he also supported his cousin Frederick I Barbarossa in their wars against the independent city communes of the Lombard League. Boniface's eldest brother, William, had died in 1177, soon after marrying Sibylla, the heiress presumptive to the Kingdom of Jerusalem. In 1179, the Byzantine emperor Manuel I Komnenos offered his daughter Maria Porphyrogenita as a bride to one of the sons of William V. Since Boniface, like his older brother Conrad, was already married, and Frederick was a priest, the youngest brother, Renier, married her instead, only to be murdered along with her during the usurpation of Andronikos. In 1183, Boniface's nephew Baldwin V was crowned co-king of Jerusalem. William V went out to the kingdom to support his grandson, leaving Conrad and Boniface in charge of Montferrat. However, in 1187, Conrad also left for the East: Isaac II Angelos had offered his sister Theodora to Boniface as a wife, to renew the family's Byzantine alliance, but Boniface had just married for the second time, while Conrad was a recent widower. In 1189, Boniface joined the council of regency for Thomas I of Savoy, son of his cousin Humbert III, until the boy came of age about two years later. In 1191, after the new Emperor Henry VI granted him the county of Incisa,