Olga Nikolaevna of Russia was Queen of Württemberg from 25 June 1864 until 6 October 1891 as the wife of Charles I of Württemberg.

Charles was King of Württemberg from 25 June 1864 until his death in 1891. Charles I married Grand Duchess Olga Nikolaevna of Russia in 1846 and ascended to the throne in 1864. Despite their marriage, the couple had no children, likely due to Charles' homosexuality. Charles was involved in several scandals, including a close relationship with American Charles Woodcock. In 1870, the couple adopted Olga's niece, Vera Konstantinovna. Charles I aligned with Austria during the Austro-Prussian War but later sided with Prussia in the Franco-Prussian War, joining the new German Empire in 1870. He died childless and was succeeded by his nephew, William II.