William II, Count of Hainaut

William II, Count of Hainaut (1307 – 26 September 1345 at Warns, near Stavoren) was William IV of Avesnes, William IV of Holland and William III of Zeeland from 1337 to his death, succeeding his father, William I. He married Joanna, Duchess of Brabant and Limburg in 1334, but had no issue.

Military career and death
William fought in France as ally of the English (he was the brother in law of Edward III). He went on crusade against the Saracens and the Lithuanians. He besieged Utrecht, because his one time favourite bishop John van Arkel of Utrecht had turned against him. He died during one of the battles of Warns against the Frisians in 1345.

After his death
William was succeeded by his sister, who was married to emperor Louis IV. Hainaut, Holland and Zeeland became a part of the imperial crown domains.