William the Good
|Count of Hainaut, Holland, and Zeeland|
|Died||7 June 1337|
|Noble family||House of Avesnes|
|Spouse(s)||Joan of Valois|
|Father||John II, Count of Hainaut|
|Mother||Philippa of Luxembourg|
William the Good (Dutch : Willem, French : Guillaume; c. 1286 – 7 June 1337) was count of Hainaut (as William I), Avesnes, Holland (as William III), and Zeeland (as William II) from 1304 to his death.
William, born c. 1286, was the son of John II, Count of Hainaut, and Philippa, daughter of Henry V, Count of Luxembourg.  He was the brother of John of Beaumont and Alice of Hainault.
William was originally not expected to become count. After the deaths of his elder brothers, John (killed at Kortrijk in 1302) and Henry (d. 1303), he became heir apparent to his father's counties. 
Prior to 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, during which the Count of Flanders renounced all claims on Zeeland. William, in turn, gained all of Zeeland but agreed to renounce all claims on Imperial Flanders.  William had occupied most of the Bishopric of Utrecht and tried to conquer Friesland but was repelled by Hessel Martena. At the death of his uncle, Guy d'Avesnes, Bishop of Utrecht, William took his fief of Amsterdam and annexed it to Holland. 
Many of his daughters married with important rulers of Europe; King Edward III of England and Holy Roman Emperor Louis IV were married to his daughters, while he was married to the sister of the King Philip VI of France.  With these important alliances William gained considerable influence and respect which he used to advance the interests of his counties. 
On 19 May 1305 William married Joan of Valois,  sister of the future king Philip VI of France,  and had the following children:
|Ancestors of William I, Count of Hainaut   |
Baldwin VI, also known as Baldwin the Good, was Count of Hainaut from 1051 to 1070 and Count of Flanders from 1067 to 1070.
John II was Count of Hainaut, Holland, and Zeeland.
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Adela of France, known also as Adela the Holy or Adela of Messines;, was, by marriage, the duchess of Normandy, and countess of Flanders (1035–1067).
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Beatrice of Vermandois was a Carolingian aristocrat, queen of Western Francia by marriage to Robert I, and mother of Hugh the Great.
Rozala of Italy was countess consort of Flanders by marriage to Arnulf II of Flanders, and queen of the Franks by marriage to Robert II of France. She was regent of Flanders in 987-988 during the minority of her son Baldwin IV of Flanders.
Judith of Brittany, also called Judith of Rennes (982–1017), was Duchess of Normandy from c. 1000 until her death.
Baldwin II of Boulogne was a son of Arnulf III, Count of Boulogne, whom he succeeded as count of Boulogne.
Ermengarde of Anjou,, was the Countess of Rennes, Regent of Brittany (992–994) and also Countess of Angoulême.
Gerberge of Lorraine was the daughter of Giselbert, Duke of Lorraine, and Gerberga of Saxony, daughter of Henry I the Fowler, King of Germany. She was a descendant of Charlemagne through both her parents. Gerberge died sometime after 7 September 978.