Marius et Fanny is an opera (opéra comique) in two acts composed by Vladimir Cosma.
The opera premiered on 4 September 2007 at the Opéra de Marseille with Roberto Alagna and Angela Gheorghiu in the title roles.
Marius abandons her, and she marries her elderly admirer, Honoré Panisse, to provide a father for her baby.
When Marius returns from sea and finds Fanny married, he tries to win her back, but to no avail.
Their son, Césariot, is being raised as Panisse's legitimate child, and in the intervening years, Fanny has been transformed into "the perfect bourgeois wife".