A critical review of the Argentinian, Uruguayan, and Paraguayan species of Acalypha L. (Euphorbiaceae) is presented. As a result, 18 species (22 taxa) are accepted, 16 from Argentina, 12 from Paraguay, and five from Uruguay, and 49 names are considered as synonyms. Typifications are provided for A. brasiliensis Müll. Arg., A. cordobensis Müll. Arg., A. friesii Pax & K. Hoffm., A. gracilis Spreng., A. nitschkeana Pax & K. Hoffm., A. multicaulis Müll. Arg. var. glabrescens Pax & K. Hoffm., A. lagoensis Müll. Arg. var. grandifolia Chodat & Hassl., and A. striolata Lingelsh. Identification keys are also provided as are original illustrations of three species and distribution maps of all the accepted taxa.