Foundation species, originally defined by Dayton (1972), are those species that are important to the community and processes in ecosystems beyond their abundance (at the same time, however, they usually reach high biomass). They create a habitat for other species, affect the nutrient cycle, energy flow and the nature of interspecific interactions throughout the ecosystem. The aim of my bachelor's thesis was to review published scientific articles on the foundation species with a focus on freshwater foundation species. The thesis is based on systematic literature research in the Web of Science database. Among the reviewed papers, only 15 studies were focused on freshwater foundation species. Based on my theoretical research, I dare to say that freshwater foundation species still appear as Terra Incognita the map of knowledge of the importance of freshwater foundation species still contains many white spots.