The southern South American genus Brachysternus Guérin-Méneville is revised and now includes seven species: B. angustus (Philippi and Philippi), B. germaini (Ohaus) new combination, B. marginatus Germain, B. olivaceus Philippi and Philippi, B. patagoniensis Jameson and Smith new species, B. prasinus Guérin-Méneville, and B. spectabilis Erichson. The following species names are new synonyms of B. prasinus: B. vicinus Guérin-Méneville, B. sinuatifrons Germain, B. pubescens Germain, B. viridis Germain, B. dilatatus Germain, B. viridipes Ohaus, and B. hirtus Ohaus. The following species names are new synonyms of B. olivaceus: B. chloris Philippi and Philippi, B. riverae Germain, B. herbaceus Germain, and B. araucanicus Ohaus. The following names were incorrect: “B. viridis Guérin-Méneville” (lapsus calami), “B. viridis Laporte” (lapsus calami), “B. viridis Solier” (incorrect author), and “B. fulvescens Germain” (misapplication). Lectotypes are designated for the following names: B. araucanicus Ohaus, B. chloris Philippi and Philippi, B. dilitatus Germain, B. fulvipes Guérin-Méneville, B. hirtus Ohaus, B. marginatus Germain, B. obscurus Philippi and Philippi, B. olivaceus Philippi and Philippi, B. philippii Germain, B. pubescens Germain, B. riverae Germain, B. spectabilis Erichson, B. vicinus Guérin-Méneville, B. viridipes Ohaus, and B. viridis Germain. Neotypes are designated for B. germaini (Ohaus) and B. prasinus Guérin-Méneville. Keys to adults, diagnostic characters, descriptions, and distributions are presented.