William I of Montferrat was a nobleman from the House of Montferrat, ruling from 1191 until his death in 1225. He was the son of Boniface I of Montferrat and Cecilia of Italy, and he played a significant role in the politics of northern Italy during the late 12th and early 13th centuries. His reign was marked by efforts to strengthen his family's influence and territorial control. William I is also known for his involvement in the Crusades, particularly the Fourth Crusade, which aimed to reclaim the Holy Land. He was a key figure in the region, navigating alliances and conflicts with neighboring powers, including the Holy Roman Empire and various Italian city-states. His leadership helped solidify the Montferrat family's status in medieval Europe.