The genus Copelatus Erichson, 1832 (Coleoptera, Dytiscidae, Copelatinae) of Madagascar is revised intwo parts. This review is restricted to the Copelatus species that have fewer than ten elytral + one submarginalstria, including all species except those of the erichsonii species group. Both morphological andmolecular (mitochondrial COI) data are used in an integrative taxonomic approach. Thirteen speciesare recognised, of which five are described as new: Copelatus ankaratra sp. nov., Copelatus kely sp. nov.,Copelatus pseudostriatus sp. nov., Copelatus safiotra sp. nov. and Copelatus vokoka sp. nov. Copelatus unguicularisRégimbart, 1903 and Copelatus apicalis Fairmaire, 1898 are both transferred to the genus MadaglymbusShaverdo & Balke, 2008 (comb. nov.). Copelatus mimetes Guignot 1957 is a junior synonym ofthe widespread Afrotropical–Arabian Copelatus pulchellus (Klug, 1834) (syn. nov.). Copelatus marginipennis(Laporte, 1835) is reinstated (stat. nov.) as a valid species with Copelatus aldabricus Balfour-Browne,1950 and Copelatus aldabricus var. simplex Guignot, 1952 as junior synonyms (syn. nov.). We designatelectotypes for Colymbetes marginipennis Laporte, 1835 and Copelatus obtusus Boheman, 1848. Copelatusperidinus Guignot, 1955 is recorded for Madagascar for the first time and Copelatus nodieri Régimbart,1895 is rejected as a species present in Madagascar.