Princess Cecilie of Greece and Denmark was by birth a Greek and Danish princess who became titular Hereditary Grand Duchess of Hesse and by Rhine through her marriage to Prince Georg Donatus, pretender to the throne of the Grand Duchy of Hesse. She was also the third-eldest sister to Prince Philip of Greece and Denmark.

Georg Donatus, Hereditary Grand Duke of Hesse was the first child of Ernest Louis, Grand Duke of Hesse, and his second wife, Princess Eleonore of Solms-Hohensolms-Lich. He was a nephew of Empress Alexandra and Emperor Nicholas II of Russia.