William Longsword of Montferrat

William Longsword, Italian byname Spadalunga (1140s–April 1177), was the eldest son of Marquis William V of Montferrat. In 1176 the High Court of Jerusalem chose him to marry Sibylla, sister and heir presumptive of the leper king Baldwin IV. Landed at Sidon by a Genoese fleet that October, he wed Sibylla despite noble opposition and received Jaffa and Ascalon as the likely heir to the throne.

He died of illness at Ascalon only months later, in April 1177, leaving Sibylla pregnant with the future Baldwin V; rumor said he had been poisoned.