Countess Alexandra Constantinovna von Zarnekau (Russian: графиня Александра Константиновна Зарнекау, 10 May [O.S. 28 April] 1883 – 28 May 1957) was the eldest daughter of Duke Constantine Petrovich of Oldenburg and his Georgian wife, Princess Agrippina Japaridze, Countess von Zarnekau, formerly married to the Georgian Prince Dadiani.