Duke Alexander Petrovich of Oldenburg

Duke Alexander Frederick Constantin of Oldenburg (; , Alexander Petrovich Oldenburgsky; – 6 September 1932) was the second son of Duke Peter of Oldenburg and his wife, Princess Therese of Nassau-Weilburg. Though he had a German title and ancestry, Alexander and his siblings were born and raised in St. Petersburg as the grandchildren of Grand Duchess Catherine Pavlovna of Russia.