Louis Simon Denise (5 June 1863, Paris – 30 June 1914, Paris) was a French librarian and ornithologist.
During his career, he served as head librarian at the Bibliothèque nationale de France in Paris. With Auguste Ménégaux, he published the ornithological journal, Revue française d'ornithologie scientifique et pratique (from 1910). His name is associated with Atlapetes semirufus denisei, a subspecies of ochre-breasted brush finch that was circumscribed by Carl Eduard Hellmayr (1911).
In 1889 he took part in the creation of the modern Mercure de France. He participated in the Le Chat Noir, a nineteenth-century entertainment establishment, and was a good friend of the poets Albert Samain and Louis Le Cardonnel and of the novelist Léon Bloy.
With Francisque Vial, he published works in regards to literary ideas and doctrines of the 17th, 18th and 19th centuries: