Lysimachia is a genus that was recently recircumscribed and greatly enlarged by the inclusion of many genera in the Primulaceae. In this work five new species, all endemic from the grasslands of southern Brazil, are described, two new combinations are proposed, and 10 typifications are effected. The preliminary conservation status of these species are assessed, and we also provide field photographs and distribution maps. Furthermore, we provide an identification key to all species of Lysimachia that occur in Brazil.