Willem (Dillenburg, April 24, 1533 – Delft, July 10, 1584), Prince of Orange, Count of Nassau-Dillenburg, better known as William of Orange or under his posthumous nickname William the Silent, was a statesman and army commander who played a key role in the unleashing of the Eighty Years' War and the foundation of the resulting Republic of the Seven United Netherlands. Previously, he was in the service of the ruler against whom this war had started as a rebellion, the Spanish king Philip II. Orange had started his career with his father, Emperor Charles V. In the Netherlands he is known as the Father of the Fatherland. His original name is Wilhelm. Willem is his Dutchest name. The name William of Orange came about because he inherited the title Prince of Orange in 1544.
Part of one of his mottoes was Je maintiendrai (French for 'I will maintain'), which was enshrined in the coat of arms of the Kingdom of the Netherlands. The national anthem of the later state of the Netherlands has been named after him since 1932: the Wilhelmus. Dutch sports teams have worn orange nationally since the twentieth century, which can be traced back to his title of Prince of Orange.
Source: Wikipedia