Louise of Hesse-Kassel (German: Luise Wilhelmine Friederike Caroline Auguste Julie, Danish: Louise Vilhelmine Frederikke Caroline Auguste Julie; 7 September 1817 – 29 September 1898) was Queen of Denmark as the wife of King Christian IX from 15 November 1863 until her death in 1898.

As children, her brother Frederick Wilhelm, her sisters and she were the closest relatives of King Christian VIII who were likely to produce heirs.

It was increasingly obvious that the traditional male line succession might come to an end within a generation as the crown prince was childless despite two marriages.

Denmark and its fief Schleswig both followed the succession rules in the King's Law giving Louise a strong claim to the Danish throne.

The House of Augustenborg argued that the King's Law was purely agnatic and presented itself as the opportunity to preserve the undivided monarchy.

The situation remained disputed and succession was a main reason for the House of Augustenburg rebelling against Denmark in the 1848–51 First Schleswig War.

By 1853, Denmark had become a constitutional monarchy and Parliament amended the Danish law of succession proclaiming Christian Hereditary Prince of Denmark, thus cementing that he would succeed when King Frederick VII died (unless the uncle of King Frederick, Prince Ferdinand, would outlive his nephew).

She took no part in state affairs; her political interests focused on the arranged dynastic marriages of her children and were affected by her anti-German views.

In 1857, she founded the Louisestiftelsen (Louise Foundation), an orphanage for girls with the purpose of raising them to a life of domestic servants, which illustrated her deeply conservative ideals.

In 1891, she initiated the Foreningen til Oprettelse af Friskolebørneasyler i Kbh.s Arbejderkvarter (Foundation for the Establishment of Charter school's Asylums in the Labour Quarters of Copenhagen).

She founded the Belønnings- og Forsørgelsesforeningen (The Reward- and Self-supporting Foundation) in 1881, supported domestic servants by providing financial aid to the ill, during unemployment and in retirement.

Queen Louise died peacefully at Bernstorff Palace aged 81 on 29 September 1898 and was interred in Roskilde Cathedral near Copenhagen on 15 October 1898.