William I, Prince of Orange (24 April 1533 – 10 July 1584), also widely known as William the Silent (Dutch: Willem de Zwijger), or simply William of Orange (Dutch: Willem van Oranje), was the main leader of the Dutch revolt against the Spanish that set off the Eighty Years' War and resulted in the formal independence of the United Provinces in 1648. He was born in the House of Nassau as Count of Nassau-Dillenburg. He became Prince of Orange in 1544 and is thereby the founder of the branch House of Orange-Nassau.

A wealthy nobleman, William originally served the Habsburgs as a member of the court of Margaret of Parma, governor of the Spanish Netherlands. Unhappy with the centralisation of political power away from the local estates and with the Spanish persecution of Dutch Protestants, William joined the Dutch uprising and turned against his former masters. The most influential and politically capable of the rebels, he led the Dutch to several successes in the fight against the Spanish. Declared an outlaw by the Spanish king in 1580, he was assassinated by Balthasar Gérard (also written as 'Gerardts') in Delft four years later.

Prince of Orange is a title of nobility, originally associated with the Principality of Orange, in what is now southern France. In French it is la Principauté d'Orange.

The title is carried by members of the House of Orange-Nassau, as heirs to the crown of the Netherlands. Rival claims to the title are made by members of the House of Hohenzollern and the family of Mailly. The current holders of the title are Prince Willem-Alexander of the Netherlands (Orange-Nassau), Georg Friedrich, Prince of Prussia (Hohenzollern), and Guy, Marquis de Mailly-Nesle (Mailly).

The title originally referred to Orange, Vaucluse in the Rhone valley in southern France, which was a property of the House of Orange, then the House of Baux and the House of Châlon-Arlay before passing in 1544 to the House of Orange-Nassau.

The area started as the County of Orange, a fief in the Holy Roman Empire, in its constituent Kingdom of Burgundy. It was awarded to William of Gellone, a grandson of Charles Martel and therefore a cousin of Charlemagne, around the year 800 for his services in the wars against the Moors and reconquering southern France and the Spanish March. His Occitan name is Guilhem. However, as a Frankish lord, he probably knew himself by the old Germanic version of Wilhelm. William was also count of Toulouse, duke of Aquitaine, and marquis of Septimania. The horn that came to symbolize Orange when heraldry came in vogue much later in the 12th century was a pun on his name in French, from the character his deeds inspired in the chanson de geste, the Chanson de Guillaume, "Guillaume au Court Nez" or "Guillaume au Cornet". The chanson appears to be based on William of Gellone's battle at the Orbieu or Orbiel river near Carcassonne in 793 as well as his seizure of the town of Orange.

William III & II (Dutch: Willem III; 4 November 1650 – 8 March 1702) was a sovereign Prince of Orange of the House of Orange-Nassau by birth. From 1672 he governed as Stadtholder William III of Orange (Dutch: Willem III van Oranje) over Holland, Zeeland, Utrecht, Guelders, and Overijssel of the Dutch Republic. From 1689 he reigned as William III over England and Ireland. By coincidence, his regnal number (III) was the same for both Orange and England. As King of Scotland, he is known as William II. He is informally known in Northern Ireland and Scotland as "King Billy". In what became known as the "Glorious Revolution", on 5 November 1688 William invaded England in an action that ultimately deposed King James II & VII and won him the crowns of England, Scotland and Ireland. In the British Isles, William ruled jointly with his wife, Mary II, until her death on 28 December 1694. The period of their joint reign is often referred to as "William and Mary".

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. Largely because of that reputation, William was able to take the British crowns when many were fearful of a revival of Catholicism under James. William's victory over James at the Battle of the Boyne in 1690 is commemorated by the Orange Institution in Northern Ireland and parts of Scotland to this day. His reign marked the beginning of the transition from the personal rule of the Stuarts to the more Parliament-centred rule of the House of Hanover.

William Nicholas Alexander Frederick Charles Henry, Prince of Orange, Prince of the Netherlands, Prince of Orange-Nassau (Dutch: Willem Nicolaas Alexander Frederik Karel Hendrik, Prins van Oranje, Prins der Nederlanden, Prins van Oranje-Nassau; The Hague, 4 September 1840 – Paris, 11 June 1879), was heir apparent to his father King William III of the Netherlands from 17 March 1849 until his death.

Prince William was the eldest son of King William III of the Netherlands and his first wife, Princess Sophie of Württemberg. His nickname was Wiwill. At his birth, he held the third position in the line of succession to the Dutch throne and the seventeenth position in the line of succession to the British throne. A month afterwards on 7 October 1840, his great-grandfather, the reigning King William I of the Netherlands, abdicated the throne due to the disappointment over the recent Treaty of London, which recognised the independence of Belgium (previously provinces of the United Kingdom of the Netherlands), and the intention of marrying a Roman Catholic and Belgian noblewoman, Henrietta d'Oultremont. In 1849, after the death of his grandfather King William II of the Netherlands, he became the heir apparent. His Victorian upbringing turned out to be a disaster.