Prince Sergey Konstantinovich Beloselsky-Belozersky, born on July 25, 1867, and died on April 20, 1951, was a Russian aristocrat, general, and member of the International Olympic Committee, as well as one of the largest landowners in Russia. He graduated from the Imperial Cadet Corps in 1887 and began his service as a cornet in the Life Guards, later working at Russian embassies in Berlin and Paris.

Sergey left military service in 1894 but returned to it in 1895. From 1896 to 1905, he served as aide-de-camp to Grand Duke Vladimir Alexandrovich. From 1908, he commanded the 3rd Novorossiysk Dragoon Regiment, and from 1913, the Imperial Guard Uhlans. He owned an estate on Krestovsky Island, where in 1908, Nikolai, the brother of Felix Yusupov, was killed in a duel.

During World War I, Sergey Konstantinovich commanded the 2nd Guards Cavalry Division and the 3rd Don Cavalry Division. From 1915, he served on the Caucasian Front under General Nikolai Baratov. In 1917, he joined the White movement and served on the staff of the leader of the White Finns, Carl Gustav Emil Mannerheim, during the Russian Civil War. Later, he became a staff officer of the Northwestern Army of General Yudenich.

After the Civil War, Prince Sergey settled in England and died in 1951 in Tonbridge, where he befriended Denton Welch. Sergey was an avid sportsman and one of the founders of the St. Petersburg Sports Club, representing Russia in the International Olympic Committee from 1900 to 1908. He is buried in the cemetery in Tonbridge, plot 34, grave 5660.