Marthe de Florian (born Mathilde Héloïse Beaugiron; 9 September 1864 – 29 August 1939) was a French demi-mondaine and socialite during the Belle Époque.

She was known for having famous lovers including Georges Clemenceau, Pierre Waldeck-Rousseau, Paul Deschanel, Gaston Doumergue, Robert de Montesquiou, and Giovanni Boldini.

Initially forgotten from history, her story resurfaced in 2010 after her belongings were discovered in her Parisian apartment, located at 2 square La Bruyère in the 9th arrondissement, untouched for decades.

[citation needed] On 12 October 1882, at the age of 18, she gave birth to her first son, Henri Beaugiron, whose paternity was unknown and who was born at 69 Rue Condorcet in the 9th arrondissement.

During World War II de Florian's granddaughter, Solange, escaped from the Nazis and settled in the South of France, never to come back to clear the apartment after her father's death in 1966.