The Night Is Young

Austrian Emperor Franz Josef has arranged a marriage for his nephew, the Archduke Paul Gustave - nicknamed Gustl - to the suitable Princess Matilda, a woman Gustl can't even remember. He is instead in love with the Hungarian Countess Zarika Rafay, which Gustl can't tell his uncle since he disapproves of her family. The Emperor will allow Gustl to sow his wild oats before getting married, but that woman needs to be someone "harmless" outside of the royal circle. (imdb)