William I, Duke of Bavaria-Straubing (Frankfurt am Main, 12 May 1330 – 15 April 1389,[1] Le Quesnoy), was the second son of Emperor Louis IV and Margaret II of Hainaut.

Edward III shortly afterwards changed sides, and the empress saw herself compelled (1354) to come to an understanding with her son, he being recognized as count of Holland and Zeeland, she of Hainaut.

In 1357, on returning from a trip to England, William began to show signs of insanity,[2] going so far as to attack and kill one of his knights (Gerard van Wateringe) for no apparent reason, before he could be restrained.

He was, truly, young and tall, strong and swarthy and agile, more fleet and dexterous than any man in his land, and he had married the daughter of the worthy and valiant Duke of Lancaster; but he was curiously distant and inscrutable: he wouldn't welcome or acknowledge people in the manner of a great prince, and took no pleasure in the company of ladies or damsels, at feasts or otherwise; nor did he have any close confidants (except just one, called master Thierry); and you could never be quite sure whether you were in favor with him or not.

And in the end, not long after he'd arranged the peace between the Count of Flanders and the Duke of Brabant, he lost his wits entirely, and most of the time he had to be bound hand and foot.