August Ludwig, Baron von Senarclens de Grancy (19 August 1794 – 3 October 1871) was born Auguste Louis de Senarclens de Grancy at the château d'Etoy in the canton of Vaud, Switzerland (ancestral home of the de Loriol family), the firstborn son of three sons and four daughters of César Auguste, Baron von Senarclens de Grancy, (born in 1763) and wife Élizabeth Claudine Marie-Rose de Loriol (born in 1773). He is reputed to have been the long-time lover of Wilhelmine of Baden, the Grand Duchess consort of Hesse, and the actual father by her of the Empress consort Maria Alexandrovna of Russia and Prince Alexander of Hesse, ancestors of modern royalty in Bulgaria, Germany, Romania, Serbia, Spain, Sweden and the United Kingdom.
He became the stable master of Louis II, Grand Duke of Hesse, a major general and a knight in the Order of Malta. It is also alleged that he was the biological father of four of the children of his employer's wife and, therefore, a likely ancestor of Felipe VI of Spain and Charles, Prince of Wales, heir apparent to the throne of the United Kingdom. He may also be a direct-line ancestor of several royal pretenders: Alexander, Crown Prince of Yugoslavia, King Michael of Romania and Georg Friedrich, Prince of Prussia, heir to the throne of the German Empire which collapsed at the end of World War I.
Louis II, Grand Duke of Hesse, bought the property of Heiligenberg near Jugenheim in 1820, installing his chamberlain, Senarclens de Grancy, there. From the year of that acquisition Grand Duchess Wilhelmine no longer lived with her consort, with whom she had not had any children since 1809, and proceeded to give birth four times between 1821 and 1824. Senarclens's identity as the father of the later children of Wilhelmine was strongly suspected: correspondence asserting or repeating the allegation was recorded by several government ministers, ambassadors and sovereigns, including Tsar Nicholas I and Queen Victoria.
By Wilhelmina, Senarclens de Grancy is believed to have fathered four children during her marriage to Grand Duke Louis:
- Princess Amalia Elisabeth Luise Karoline Friederike Wilhelmine of Hesse-Darmstadt (20 May 1821 – 27 May 1826).
- Stillborn daughter (7 June 1822).
- Prince Alexander Ludwig Georg Friedrich Emil of Hesse and by Rhine (15 July 1823 – 15 December 1888), morganatically married to Countess Julie Hauke, she and their children being elevated to the title of princess/prince of Battenberg.
- Princess Maximiliane Wilhelmine Auguste Sophie Marie of Hesse and by Rhine (8 August 1824 – 3 June 1880); the future Empress consort of Tsar Alexander II of Russia.
Alexander and Marie were the only two to survive childhood and remained legally the children of Wilhelmina's husband, Grand Duke Louis II, who neither denied paternity nor sought to disinherit any of the children to whom his wife gave birth, even after the death of the Grand Duchess. Alexander and Marie are ancestors of the last emperors of Russia, as well as the princely Battenbergs (now known as the Mountbattens).
In 1836, the same year of Grand Duchess Wilhelmine's death, he married Luise Wilhelmine Camille von Otting und Fünfstetten (24 May 1810 – 1876), said to be a morganatic descendant of the Counts Palatine of Zweïbrucken and the Margraves of Baden-Durlach, by whom he had three sons and three daughters:
- Baroness Wilhelmine von Senarclens de Grancy (11 August 1837 – 1912), unmarried.
- Baron Ludwig von Senarclens de Grancy (9 June 1839 – 2 February 1910), married Amalie Barbara, Baroness Löw von und zu Steinfurth.
- Baroness Marie Wilhelmine von Senarclens de Grancy (9 June 1840 – 5 July 1908), married Ludwig Heinrich von Hesse.
- Baron Henri Adolphe Louis von Senarclens de Grancy (1845 – died young).
- Baron Albert Ludwig Friedrich von Senarclens de Grancy (9 February 1847 – 20 January 1901), married his kinswoman Antoinette von Senarclens de Grancy.
- Baroness Constance von Senarclens de Grancy (11 September 1852 – 9 March 1933), married Karl von Oertzen.
He died at Jugenheim.