William III (; 4 November 1650 – 8 March 1702), also widely known as William of Orange, was sovereign Prince of Orange from birth, Stadtholder of Holland, Zeeland, Utrecht, Gelderland, and Overijssel in the Dutch Republic from 1672, and King of England, Ireland, and Scotland from 1689 until his death. It is a coincidence that his regnal number (III) was the same for both Orange and England. As King of Scotland, he is known as William II. He is sometimes informally known in Northern Ireland and Scotland as "King Billy". 

William inherited the principality of Orange from his father, William II, who died a week before William's birth. His mother Mary, Princess Royal, was the daughter of King Charles I of England. In 1677, he married his fifteen-year-old first cousin, Mary, the daughter of his maternal uncle James, Duke of York. 

A Protestant, William participated in several wars against the powerful Catholic king of France, Louis XIV, in coalition with Protestant and Catholic powers in Europe. Many Protestants heralded him as a champion of their faith. In 1685, his Catholic father-in-law, James, Duke of York, became king of England, Ireland and Scotland. James's reign was unpopular with the Protestant majority in Britain. William, supported by a group of influential British political and religious leaders, invaded England in what became known as the "Glorious Revolution". On 5 November 1688, he landed at the southern English port of Brixham. James was deposed and William and Mary became joint sovereigns in his place. They reigned together until her death on 28 December 1694, after which William ruled as sole monarch.
What do the Irish in the north call him?
 "King Billy