Ludwig IV, Grand Duke of Hesse and by Rhine, K.G. (12 September 1837 in Bessungen, now Darmstadt - 13 March 1892 in Darmstadt), the ruler of the small German grand duchy of Hesse-Darmstadt (Hesse and by Rhine), was the husband of Princess Alice of Great Britain and Ireland, the second daughter of Queen Victoria and Prince Albert of Saxe-Coburg-Gotha. His children and grandchildren married into the imperial and royal houses of Russia, Germany, Great Britain, and Greece. One of his grandsons was Louis Mountbatten, 1st Earl Mountbatten of Burma and one his great grandsons is Prince Philip, Duke of Edinburgh, the consort of Elizabeth II of the United Kingdom.

His Grand Ducal Highness Prince Friedrich Wilhelm Ludwig Karl, was born at Darmstadt, the son of Prince Karl of Hesse and by Rhine (23 April 1809-20 March 1877) and Princess Elizabeth of Prussia (18 June 1815-21 March 1855). Prince Ludwig was a nephew of Ludwig III, Grand Duke of Hesse and by Rhine (9 June 1806-13 June 1877); of Prince Alexander of Hesse and by Rhine (15 July 1823-15 December 1888), from whom the Battenberg and the Mountbatten families descended; and Princess Marie of Hesse and by Rhine (8 August 1824-3 June 1880), who married Tsar Alexander II of Russia.

On 1 July 1862 at Osbourne House on the Isle of Wight, Prince Ludwig married Her Royal Highness the Princess Alice, the second daughter of Queen Victoria. On the day of the wedding, the Queen issued Letters Patent granting her new son-in-law the style of Royal Highness. This style was only in effect in Great Britain, not the German confederation where Prince Ludwig was only a Grand Ducal Highness. The Queen subsequently created him a Knight of the Garter. Their Royal Highness Prince and Princess Ludwig of Hesse had seven children:

• Princess Victoria (5 April 1863-24 September 1950) m. her cousin HSH Prince Louis of Battenberg, later 1st Marquess of Milford-Haven (24 May 1854-11 September 1921), and had issue.
• Princess Elizabeth (1 November 1864-17 July 1918), took the name Elizabeth Feodorovna on her baptism into the Russian Orthodox Church, m. her cousin HIH The Grand Duke Sergei of Russia (11 May 1857-17 February 1905), the fifth son of Tsar Alexander II and Empress Maria Alexandrovna, nee Princess Marie of Hesse and by Rhine, and had no issue.
• Princess Irene (11 July 1866-11 November 1953) m. her cousin HRH Prince Heinrich of Prussia (14 August 1862-20 April 1929), the second son of Victoria, Princess Royal and the German Emperor Friedrich III and had issue.
• Prince Ernst Ludwig (25 November 1868-9 October 1937), succeeded his father as Grand Duke of Hesse and by Rhine, 13 March 1892, forced to abdicate 9 November 1918; m. 1st (divorced 1901) his first cousin HRH Princess Victoria Melita of Great Britain and of Saxe-Coburg-Gotha (25 November 1876-2 March 1936), the second daughter of Prince Alfred, Duke of Edinburgh and later reigning Duke of Saxe-Coburg-Gotha; m. 2nd HH Princess Eleonore zu Solms-Hohensolms-Lich (17 September 1871-16 November 1937), and had issue.
• Prince Friedrich (7 October 1870-29 May 1873).
• Princess Alix (6 June 1872-17 July 1918), took the name Alexandra Feodorovna on her baptism into the Russian Orthodox Church, m. HIM Tsar Nicholas II of Russia (18 May 1868-17 July 1918).
• Princess Marie (24 May 1874-16 November 1878).

During the Austro-Prussian War of 1866, Prince Ludwig commanded the Hessian cavalry in support of the Austrian side. Following Austria's defeat, Grand Duke Ludwig III switched his allegiance to Prussia. In the 1870-71 Franco-Prussian War, Prince Ludwig led the Hessian contingent of the armies of the North German Confederation. On 13 June 1877, he succeeded his uncle as Grand Duke of Hesse taking the name Ludwig IV.

Following the death of Princess Alice in 1878, Ludwig IV contracted a morganatic marriage on 30 April 1884 with Alexandrina Hutten-Czapska (3 September 1854-8 May 1941), the former wife of Alexander Kolémine, the Russian chargé d'affaires in Darmstadt. His second wife received the title Countess von Romrod. The marriage, which caused great concern within his family, was annulled within a year. Grand Duke Ludwig IV died on 13 March 1892 and was succeeded by his son, Ernst Ludwig. His remains are buried at Rosenhöhe, the mausoleum for the Grand Ducal House of Hesse outside of Darmstadt.