The House of Orange-Nassau (in Dutch: Huis van Oranje-Nassau), a branch of the German House of Nassau, has played a central role in the political life of the Netherlands — and at times in Europe — since William I of Orange (also known as "William the Silent" and "Father of the Fatherland") organized the Dutch revolt against Spanish rule, which after the Eighty Years' War led to an independent Dutch state.

Several members of the house served during this war and after as governor or stadtholder (Dutch stadhouder). However, in 1815, after a long period as a republic, the Netherlands became a monarchy under the House of Orange-Nassau.

The dynasty was established as a result of the marriage between Hendrik III of Nassau-Breda from Germany and Claudia of Châlon-Orange from French Burgundy. Their son René of Châlon first adopted the new family name "Orange-Nassau". William I was his nephew and successor.

In the late 17th century, the family also supplied a British monarch, King William III who is credited with causing the Glorious Revolution. People around the world still celebrate his battlefield endeavors and the progress in constitutional democracy brought about through his reign, namely in the Bill of Rights 1689, every year in a controversial festival commonly called "The Twelfth".