Princess Louise Marguerite of Prussia, later the Duchess of Connaught (25 July 1860 - 14 July 1917) was the wife of Prince Arthur, Duke of Connaught, the third son and seventh child of Queen Victoria of the United Kingdom and Prince Albert of Saxe-Coburg-Gotha. A Prussian princess who married into the British Royal Family at the age of 19, the Duchess of Connaught is mainly remembered for accompanying her husband, a career army officer, to Malta, India, South Africa, and finally to Canada, where he was governor general from 1911 to 1916.

Her Royal Highness Princess Luise Marguerite Alexandra Victoria Agnes was born at Marmorpalais (Marble Palace) near Potsdam, Germany, the third daughter of Field Marshal Prince Friedrich Karl of Prussia (1828-1888) and Princess Marie of Anhalt-Dessau (1837-1906). Her father, a nephew of the German Emperor Wilhelm I, distinguished himself as a field commander during the Battle of Metz and the campaigns west of Paris in the 1870-71 Franco-Prussian War.

On 13 March 1879, Princess Luise Marguerite married the Duke of Connaught at St. George's Chapel Windsor. The Duke and Duchess of Connaught had three children:

• Princess Margaret of Connaught (15 January 1882 - 1 May 1920); married 15 June 1905 then-Crown Prince Gustav Adolph of Sweden (11 November 1882 - 15 September 1973); and had issue.
• Prince Arthur of Connaught (13 January 1883 - 12 September 1938); married 15 October 1913 his cousin Princess Alexandra, Duchess of Fife (17 May 1891 - 26 February 1959; and had issue.
• Princess Patricia of Connaught (17 March 1886 - 12 January 1974); married 27 February 1919 Sir Alexander Ramsay (29 May 1881 - 8 October 1972; and had issue.

The Duchess of Connaught spent the first twenty years of her marriage accompanying her husband on his various deployments throughout the British empire. The Duke and Duchess of Connaught acquired Bagshot Park in Surrey as their country home and after 1900 used Clarence House as their London residence. She accompanied her husband to Canada in 1911, when he began his term as governor general. In 1916, she became colonel-in-chief of the 199th Canadian (Overseas) Infantry Battalion (The Duchess of Connaught's Own Irish-Canadian Rangers), CEF. In 1885, she became chief of the 64th (8th Brandenburg) Regiment of Infantry "Field Marshal General Prince Friedrich Karl of Prussia", Prussian Army.

Queen Victoria invested the Duchess of Connaught with the Order of Victoria and Albert (first class) and appointed her a Lady of the Imperial Order of the Crown of India in March 1879. The Duchess became a member of the Red Royal Cross in 1883 and was invested as a Dame of Justice of the Most Venerable Order of St. John of Jerusalem in 1888.

The Duchess of Connaught died of influenza and bronchitis at Clarence House, a causalty of the 1917-18 influenza epidemic. She was buried in the Royal Mausoleum, Frogmore, Windsor. The Duke of Connaught survived her by almost twenty-five years.