Charles Isidore Douin (1858 – 1944) was a French bryologist who was a native of Bouville, Eure-et-Loir.

[1] He taught school in Chartres, and was the author of a highly regarded work on mosses and liverworts titled Nouvelle flore des mousses et des hépatiques pour la détermination facile des espèces (1892).

He also published a book involving bryology of Eure-et-Loir, Muscinées d'Eure-et-Loir (1906).

[2] The liverwort genus Douinia from the family Scapaniaceae is named in his honor in 1928.

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