William I, Count of Hainaut (1286 – June 7 1337) was Count William III of Avesnes, Count William III of Holland and Count William II of Zeeland from 1304 to his death, succeeding his father, John II. Before becoming count, he was defeated by Guy of Namur at the battle on the island of Duiveland in 1304. Guy and Duke John II of Brabant then conquered most of Zeeland and Holland, but these territories were recovered again when William became the new count in the same year. William continued the war with Flanders until the peace of Paris in 1323, where the Count of Flanders denounced all claims on Zeeland. William had occupied most of the bishopric of Utrecht and tried to conquer Friesland. Many of his daughters married with important rulers of Europe and he was called the father in law of Europe. The King of England and the Holy Roman Emperor were married to his daughters, while he was married to the sister of the King of France. William tried to gain support of surrounding counties and duchies for an anti-French coalition. Internally, William restored order and founded new institutions, like the treasury and the chancellory. The council of the count got more responsibilities.
Family
He married Jeanne of Valois, sister of the future king Philip VI of France, in 1305 and had the following children:
- William II, Count of Hainaut (1307-1345)
- John (died 1316)
- Margaret II, Countess of Hainaut (1311-1356), married Louis IV Wittelsbach, Holy Roman Emperor
- Philippa of Hainault (1311-1369), married King Edward III of England
- Agnes (died 1327)
- Joanna of Hainaut (1315-1374), married William V, Duke of Jülich
- Isabelle of Hainaut (1323-1361), married Robert of Namur
- Louis (1325-1328)
See also
| Preceded by John II |
Count of Hainaut  |
Succeeded by William II |
Count of Holland  and Zeeland  |
