William I of Avesnes was a notable nobleman in the 13th century, serving as the Count of Hainaut and Holland. He was born around 1280 and became a significant political figure, known for his efforts to strengthen his territories and expand his influence in the region. His reign was marked by various conflicts and alliances, particularly with neighboring regions. William I played a crucial role in the Franco-Flemish War and sought to maintain peace and stability in his domains. He passed away in 1337, leaving a legacy that influenced the future of Hainaut and Holland.