The Magnificent Sinner (Katja, die ungekrönte Kaiserin)

The Magnificent Sinner, originally titled Katia in French, is a 1959 French historical drama directed by Robert Siodmak. Running about 93 minutes, it is a remake of Maurice Tourneur's 1938 film of the same name, which starred Danielle Darrieux. It draws on a novel by the French writer Princess Marthe Bibesco that freely retells the life of Yekaterina Dolgorukova.

The story centres on the romance between Tsar Alexander II of Russia and Catherine Dolgorukova, then still a schoolgirl. Katia first becomes the Tsar's mistress and in the end his morganatic wife. Romy Schneider plays Katia and Curd Jürgens plays Tsar Alexander II. The cast also includes Pierre Blanchar, Michel Bouquet, Gabrielle Dorziat, Françoise Brion, Alain Saury, Antoine Balpêtré, Bernard Dhéran and Irène Tunc.

The screenplay is by Charles Spaak and Georges Neveux. The film is known as Katja, die ungekrönte Kaiserin in German and as Катя — некоронованная царица in Russian; both titles allude to an uncrowned empress.