The Opopaea fauna of Madagascar is documented for the first time. There are 27 species of Opopaea on the island of which 26 are newly described here and 25 are apparently endemic to Madagascar: Opopaea andranomay, n. sp., O. ankarafantsika, n. sp., O. ankarana, n. sp., O. antsalova, n. sp., O. andringitra, n. sp., O. antsiranana, n. sp., O. bemarivo, n. sp., O. bemaraha, n. sp., O. berenty, n. sp., O. betioky, n. sp., O. itampolo, n. sp., O. kirindy, n. sp., O. manderano, n. sp., O. mahafaly, n. sp., O. manongarivo, n. sp., O. namoroka, n. sp., O. sandranantitra, n. sp., O. torotorofotsy, n. sp., O. tsimaloto, n. sp., O. tsimbazaza, n. sp., O. tsimembo, n. sp., O. tsinjoriaky, n. sp., O. tsingy, n. sp., O. vohibazaha, n. sp., O. foulpointe, n. sp. and O. maroantsetra, n. sp. (shared with Kenya and the Comoros Islands), and O. concolor (Blackwall, 1859), a cosmopolitan species. All species are described and illustrated. An identification key to the species and maps of their distribution in Madagascar are also provided.