Louis of Nassau (January 10, 1538 – April 14, 1574) was the third son of William, Count of Nassau and Juliana of Stolberg, and the younger brother of Prince William of Orange Nassau.

Louis was a key figure in the revolt of the Netherlands against Spain and a strongly convinced Calvinist, unlike his brother William, whom he helped in various ways, including by arranging the marriage between him and his second wife Anna of Saxony. In 1569 William appointed him governor of the principality of Orange, giving him an indisputable position in French politics.