Mesnil-en-Ouche (, literally Mesnil in Ouche) is a commune in the department of Eure, northern France. The municipality was established on 1 January 2016 by merger of the 16 former communes of Ajou, La Barre-en-Ouche, Beaumesnil (the seat), Bosc-Renoult-en-Ouche, ÃÂpinay, Gisay-la-Coudre, Gouttiéres, Granchain, Jonquerets-de-Livet, Landepéreuse, La Roussière, Saint-Aubin-des-Hayes, Saint-Aubin-le-Guichard, Sainte-Marguerite-en-Ouche, Saint-Pierre-du-Mesnil and Thevray.
The commune along with another 69 communes shares part of a 4,747 hectare, Natura 2000 conservation area, called Risle, Guiel, Charentonne.
Population data refer to the commune in its geography as of January 2025.