Mathilde Kchessinska

Mathilde Marie Feliksovna Kschessinskaya (–6 December 1971 (also known as "Her Serene Highness Princess Romanova-Krasinskaya" from 1921) was a Russian ballerina from a family of Polish origin. She was known in the West as Mathilde Kschessinska or Matilda Kshesinskaya.
Her father Feliks Krzesiński and her brother both danced in St. Petersburg. She eventually attained the highest rank, that of "prima ballerina assoluta". 
Kschessinskaya was also a mistress of the future Tsar Nicholas II of Russia. She had been involved with Nicholas, from 1890, when he was a grand duke and she was just seventeen. She met him with his family after her graduation performance. They stayed lovers for three years, until Nicholas married Princess Alix of Hesse-Darmstadt—the future Empress Alexandra Fyodorovna—in 1894, shortly after the death of his father, Tsar Alexander III.