Christian IX (8 April 1818 – 29 January 1906) was King of Denmark from 15 November 1863 until his death in 1906. From 1863 to 1864, he was concurrently Duke of Schleswig, Holstein and Lauenburg.
A younger son of Frederick William, Duke of Schleswig-Holstein-Sonderburg-Glücksburg, Christian grew up in the Duchy of Schleswig as a prince of Schleswig-Holstein-Sonderburg-Glücksburg, a junior branch of the House of Oldenburg which had ruled Denmark since 1448. Although having close family ties to the Danish royal family, he was originally not in the immediate line of succession to the Danish throne. Following the early death of his father in 1831, Christian grew up in Denmark and was educated at the Military Academy of Copenhagen. After unsuccessfully seeking the hand of Queen Victoria of the United Kingdom in marriage, he married his double second cousin, Princess Louise of Hesse-Kassel, in 1842.