Ernest was the eldest son of Francis, Duke of Saxe-Coburg-Saalfeld, and Countess Augusta of Reuss-Ebersdorf. His youngest brother, Leopold Georg Christian Frederick, was later elected the first King of the Belgians. On 10 May 1803, aged 19, Ernest was proclaimed an adult because his father had become gravely ill, and he was required to take part in the government of the duchy. When his father died in 1806, he succeeded in the duchy of Saxe-Coburg-Saalfeld as Ernest III. However, he could not immediately take over the formal government of his lands, because the duchy was occupied by Napoleonic troops and was under French administration. The following year, after the Peace of Tilsit, the duchy of Saxe-Coburg-Saalfeld was reunited and restored to Ernest. This occurred through Russian pressure, since his sister Juliane was married to the brother of the Russian Tsar.
The marriage was unhappy because both husband and wife were promiscuous. As the biographer Lytton Strachey put it: "The ducal court was not noted for the strictness of its morals; the Duke was a man of gallantry, and the Duchess followed her husband's example. There were scandals: one of the Court Chamberlains, a charming and cultivated man of Jewish extraction, was talked of; at last there was a separation, followed by a divorce." Ernest and Louise were separated in 1824 and were officially divorced on 31 March 1826. As heirs to Coburg, the children remained with their father. Seven months after the divorce, in October 1826, Louise secretly married one of her lovers. She died in 1831. In Coburg on 23 December 1832, Ernest married his niece Duchess Marie of Württemberg, the daughter of his sister Antoinette. They had no children. This marriage made Marie both Prince Albert's first cousin and his stepmother. Ernest had three illegitimate children:
Berta Ernestine von Schauenstein, born to Sophie Fermepin de Marteaux. She married her first cousin Eduard Edgar Schmidt-Löwe von Löwenfels, the illegitimate son of her father's sister, Juliane.
Ernst Albert and Robert Ferdinand, twins born in 1838 to Margaretha Braun. They were created Freiherren von Bruneck in 1856.
Estates
After 1813, Ernest was a Prussian general and participated in military actions against Napoleon. He fought in the battles of Lützen and Leipzig, and drew in 1814 into the French fortress of Mainz. After the battle of Leipzig, he commanded the 5. Armeekorps. After the defeat of Napoleon in the Battle of Waterloo, the Congress of Vienna on 9 June 1815 gave him an area of 450 square kilometres with 25,000 inhabitants around the town of St. Wendel. Its area was somewhat augmented by the second Treaty of Paris. In 1816, this estate received the name of Principality of Lichtenberg. Ernest sold it to Prussia in 1834. In 1825, Frederick IV, Duke of Saxe-Gotha-Altenburg, who was the uncle of Ernest's first wife Louise, died without an heir. This resulted in a rearrangement of the Ernestine duchies. It was only as a member of the Ernestine dynasty that Ernest had a claim on the late duke's estates. However, he was at that time in the process of divorcing Louise, and the other branches used this as a leverage to drive a better bargain for themselves by insisting that he should not inherit Gotha. They reached a compromise on 12 November 1826: Ernest received Gotha, but had to cede Saalfeld to Saxe-Meiningen. He subsequently became "Ernest I, Duke of Saxe-Coburg and Gotha". Although he had given a constitution to Gotha in 1821, he did not interfere in the system of government in Gotha. At Coburg, Ernest was responsible for various construction projects, including the establishment of the Hoftheater in its new building. The Schlossplatz as it appears today is largely due to work under his rule. He is chiefly remembered for the economic, educational and constitutional development of his territories, and for the significant international position attained by the house of Coburg.
Death and burial
Ernest died on 29 January 1844 and was initially buried in the Morizkirche but later reinterred in the newly built mausoleum in .
