Born July 7, 1903, in St. Petersburg, in the family of Duke Nikolai Nikolaevich of Leuchtenberg and Maria Nikolaevna Grabbe. Great-grandson of Russian Emperor Nicholas I and great-great-grandson of French Empress Josephine Beauharnais-Bonaparte.

It is known that, during the Civil War, Sergei Nikolaevich was with his father Nikolai Nikolayevich, who began his struggle in Kiev and later was the ambassador plenipotentiary of General Pyotr Krasnov in Berlin. In 1920, like all of the members of the families of the dukes of Leuchtenberg, Sergei went into exile. Together with his parents, he went to France, where he entered the Higher Technical School in Lille.
In 1925, he received a diploma in electrical engineering, while in 1932 he graduated from the Noncommissioned Officer School of the Russian All-Military Union (ROVS).¹

In 1930, he had joined the National Union of Russian Youth, which after 1931 became known as the National Labor Union of a New Generation (NTSNP). The duke was elected honorary chairman of the NTSNP. He also headed the organization’s French department. At the end of 1933, due to internal turmoil, as well as activities of the NTSNP in France of which the ROVS disapproved, Sergei Nikolaevich was removed as chairman. Later, in the summer of 1934, Vladimir Poremsky replaced the duke as chairman of the French department.² In 1937, Nikolaevich moved to Leipzig, where his activities on behalf of the NTSNP ceased.³

With the outbreak of World War II, he began to cooperate with the Nazis. In particular, he served as an interpreter in the German 9th Army and headed the propaganda unit of the Rzhev commandant's office and at the headquarters of the 6th Army Corps.⁴ He also worked in the apparatus of the Committee for the Liberation of the Peoples of Russia (KONR).⁵ After the end of the war, he ended up in New York. He died on June 27, 1966, in Monterey, California.

Sergei Nikolaevich of Leuchtenberg
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