Louis was born at the Prinz-Karl-Palais in Darmstadt, the capital of the Grand Duchy of Hesse and by Rhine in the German Confederation, the first son and child of Prince Charles of Hesse and by Rhine (23 April 1809 – 20 March 1877) and Princess Elisabeth of Prussia (18 June 1815 – 21 March 1885), granddaughter of King Frederick William II of Prussia. As his father's elder brother Louis III (1806-1877), the reigning Grand Duke of Hesse and by Rhine, had been married to his first wife since 1833 without legitimate children and from 1868 was married morganatically, Prince Louis was the likely heir eventual to the grand ducal throne from childhood.
On 1 July 1862, Louis married Princess Alice, the third child of Queen Victoria of the United Kingdom, at Osborne House on the Isle of Wight. On the day of the wedding, the Queen issued a royal warrant granting her new son-in-law the style of Royal Highness in the United Kingdom. The Queen also subsequently made Prince Louis a knight of the Order of the Garter.
Although an arranged marriage orchestrated by the bride's father Albert, Prince Consort, the couple did have a brief period of courtship before betrothal and wed willingly, even after the death of the Prince Consort left Queen Victoria in a protracted state of grief that cast a pall over the nuptials. Becoming parents in less than a year following their marriage, the young royal couple found themselves strapped financially to maintain the lifestyle expected of their rank. Princess Alice's interest in social services, scientific development, hands-on child-rearing, charity and intellectual stimulation were not shared by Louis who, although dutiful and benevolent, was bluff in manner and conventional in his pursuits. The death of the younger of their two sons, Frittie, who was afflicted with hemophilia and suffered a fatal fall from a palace window before his third birthday in 1873, combined with the wearying war relief duties Alice had undertaken in 1870, evoked a crisis of spiritual faith for the princess in which her husband does not appear to have shared.
In 1866 the Austrians suffered defeat in the Austro-Prussian War and the Hessian grandduchy was in jeopardy of being awarded as the spoils of war to victorious Prussia, which annexed some of Austria's other allies (Hanover, Hesse-Cassel, Nassau), a fate from which Hesse-Darmstadt appears to have been spared only by a cession of territory and the close dynastic kinship between its ruler and the Emperor of Russia (Alexander II's consort, Empress Maria Alexandrovna, was the sister of Hesse's Grand Duke Louis III and of Prince Charles).
In the Franco-Prussian War provoked by Bismarck's manipulation of the Ems telegram in 1870, Hesse and by Rhine this time found itself a winning ally of Prussia's, and Prince Louis was credited with courageous military service, especially at the Battle of Gravelotte, which also afforded him the opportunity of mending the previous war's grievances with the House of Hohenzollern by fighting on the same side as his brother-in-law and future emperor, Prince Frederick of Prussia.
In March 1877, Louis became heir presumptive to the Hessian throne when his father died and, less than three months later, found himself reigning grand duke upon the demise of his uncle, Louis III.
A year and a half later, however, Grand Duke Louis was stricken with diphtheria along with most of his immediate family, from which he recovered but to which his four-year-old daughter Marie succumbed, along with his wife of 16 years. From then on, he reigned and raised his five surviving children alone.
The couple had seven children:Victoria Mountbatten, Marchioness of Milford Haven (5 April 1863 – 24 September 1950)
Grand Duchess Elizabeth Feodorovna of Russia (1 November 1864 – 18 July 1918)
Princess Irene of Prussia (11 July 1866 – 11 November 1953)
Ernest Louis, Grand Duke of Hesse and by Rhine (25 November 1868 – 9 October 1937)
Prince Friedrich of Hesse and by Rhine (7 October 1870 – 29 May 1873)
Empress Alexandra Feodorovna of Russia (6 June 1872 – 17 July 1918)
Princess Marie of Hesse and by Rhine (24 May 1874 – 16 November 1878)
During the Austro-Prussian War of 1866, Louis commanded the Hessian cavalry in support of the Austrian side. In the 1870-71 Franco-Prussian War, Louis 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".
Grand Duchess Alice having died in 1878, Louis IV contracted a morganatic marriage on 30 April 1884 in Darmstadt (on the eve of the wedding of his eldest daughter, for which Queen Victoria and other relatives of his first wife were gathered in the Hessian capital) with Countess Alexandrina Hutten-Czapska (3 September 1854 – 8 May 1941), the former wife of Aleksander Kolemin, the Russian chargé d'affaires in Darmstadt. His second wife received the title Countess von Romrod. But the couple, facing objections from the Grand Duke's in-laws, separated within a week and the marriage was annulled within three months.
Grand Duke Ludwig IV died on 13 March 1892 of a stroke in the New Palace in Darmstadt and was succeeded by his son, Ernest Louis. His remains are buried at Rosenhöhe, the mausoleum for the Grand Ducal House outside of Darmstadt.12 September 1837 – 1 July 1862: His Grand Ducal Highness Prince Louis of Hesse and by Rhine
1 July 1862 – 13 June 1877: His Royal Highness Prince Louis of Hesse and by Rhine
13 June 1877 – 13 March 1892: His Royal Highness The Grand Duke of Hesse and by Rhine
On 1 July 1862, the day of his wedding, Queen Victoria issued a royal warrant granting her new son-in-law the style of His Royal Highness. On his accession as Grand Duke on 13 June 1877 he also became styled as His Royal Highness in Hesse. United Kingdom: Knight of the Order of the Garter