Montjoie-en-Couserans (French pronunciation: [mɔ̃ʒwa ɑ̃ kuzʁɑ̃], literally Montjoie in Couserans; Occitan: Montjòi de Coserans) is a commune in the Ariège department in southwestern France, in the northwest of the Ariège department, in the Occitanie region.

Historically and culturally, the town is part of Couserans, an area with Gascon roots structured by the course of the Salat.

Included in the Ariège Pyrenees regional natural park, the town has a remarkable natural heritage: a protected area (the "crayfish streams: Artix, Moulicot and Volp") and six natural areas of ecological, faunal and floral beauty.

Montjoie-en-Couserans is a rural commune which had 1,010 inhabitants in 2020, after having experienced a sharp increase in population since 1975.

The Bastide of Montjoie was founded in 1268 by Alphonse de Poitiers, a prince of royal blood, the brother of Louis IX under a landscaping contract with the Bishop of Couserans.