William IV was Grand Duke of Luxembourg from 17 November 1905 until his death in 1912. He succeeded his father, Adolphe. Like his father, William mostly stayed out of politics despite being vested with considerable power on paper by the Constitution.

The Grand Duke of Luxembourg is the head of state of Luxembourg. Luxembourg has been a grand duchy since 15 March 1815, when it was created from territory of the former Duchy of Luxembourg. It was in personal union with the United Kingdom of the Netherlands until 1890 under the House of Orange-Nassau. Luxembourg is the world's only sovereign Grand Duchy and since 1815, there have been nine monarchs, including the incumbent, Henri.