This review covers the medicinal plants of Brazil’s southern grasslands (Campos Sulinos), highlighting their historical, ecological, and scientific importance. It defines the concept of medicinal plants and their cultural and therapeutic relevance from the time of ancient civilizations onward, demonstrating that the use of plant species in traditional medicine was essential for the development of modern pharmaceuticals and still represents the primary therapeutic resource for a large portion of the world’s population. The study addresses the botanical richness of Brazil—home to over 40,000 native plant species—and emphasizes the southern grasslands (grassland formations of the Pampa and Atlantic Forest biomes) as ecosystems that are highly biodiverse, yet threatened by land-use changes and limited scientific attention. The search revealed 271 threatened plant species in these grasslands, of which 24 have reported medicinal uses. Among these, families such as Asteraceae and Arecaceae predominate, but most lack genetic studies—a key factor in guiding conservation strategies. Few species, among them Araucaria angustifolia, Butia eriospatha, Hesperozygis ringens, and Colletia paradoxa, have been studied for genetic diversity. These studies reveal low variability and population risks resulting from fragmentation and overexploitation. The chapter concludes by highlighting the urgent need to expand ethnobotanical and genetic research, recognize traditional knowledge lost to colonization, and integrate environmental and cultural conservation efforts to ensure the sustainable use of the medicinal flora of the Campos Sulinos.