Matinée de Septembre is a controversial oil painting on canvas completed in 1911 by the French artist Paul Émile Chabas. Painted over several summers, it depicts a nude girl or young woman standing in the shallow water of a lake, prominently lit by the morning sun. She is leaning slightly forward in an ambiguous posture, which has been read variously as a straightforward portrayal of protecting her modesty, huddling against the cold, or sponge bathing. It has also been considered a disingenuous pose permitting the "fetishisation of innocence".

Paul Émile Chabas was a French painter and illustrator and member of the Académie des Beaux-Arts.