Charles (German: Karl Friedrich Alexander; 6 March 1823 – 6 October 1891) was King of Württemberg, from 25 June 1864 until his death in 1891.^[1][2]

Charles was born on 6 March 1823 in Stuttgart as the son of King William I and his third wife Pauline Therese (1800–1873).^[3] As the king's eldest son he became Crown Prince of Württemberg.

He studied in Berlin and Tübingen.

On 13 July 1846 Karl married Grand Duchess Olga Nikolaievna of Russia, the daughter of Tsar Nicholas I and Charlotte of Prussia.^[3] (Charlotte was a daughter of Frederick William III of Prussia and of Louise of Mecklenburg-Strelitz; she took the name Alexandra Feodorovna upon her marriage into the Russian imperial family.) Karl acceded to the throne of Württemberg upon his father's death in 1864.

The couple had no children, perhaps because of Karl's homosexuality.^[4] Karl became the object of scandal several times for his closeness with various men - most notoriously with the American Charles Woodcock, a former chamberlain whom Karl elevated to Baron Savage in 1888.^[5][6] Karl and Charles became inseparable, going so far as to appear together in public dressed identically. The resulting outcry forced Karl to renounce his favorite. Woodcock returned to America, and Karl found private consolation some years later with the technical director of the royal theater, Wilhelm George.^[4]

In 1870, Olga and Karl adopted Olga's niece Vera Konstantinovna, the daughter of her brother Grand Duke Konstantin.

He sided with Austria in the Austro-Prussian War of 1866, but after the battle of Sadowa concluded a secret military treaty with Prussia, and took part on her side in the Franco-Prussian War of 1870–'71, joining the new German Empire at the close of 1870.^[7]

He died, childless, in Stuttgart on 6 October 1891, and was succeeded as King of Württemberg by his sister's son, William II. He is buried, together with his wife, in the Old Castle in Stuttgart.