Marie Juliette Louvet (Pierreval, Seine-Maritime, 9 May 1867 – Paris, 24 September 1930) was the mistress of the then unmarried Prince Louis II of Monaco and was the mother of his only child, Princess Charlotte of Monaco.
Known as Juliette, Louvet was the daughter of Jacques Henri Louvet and his first wife, Joséphine Elmire Piedefer.
She married photographer Achille Delmaet, but they divorced in 1893. They had two children, Georges and Marguerite.
Juliette Louvet became an entertainer of sorts, reportedly a cabaret singer (other sources identify her as a laundress and a dressmaker), then was Prince Louis's lover. She gave birth to their daughter, Charlotte, in Constantine, Algeria, in 1898.