Abstract <p>Information about the algae of the Tapsa River in the Tapsinsky State Nature Reserve is presented for the first time. A list of algae has been compiled, including 103 specific and intraspecific taxa, which belong to 50 genera, 28 families, and 6 divisions. It has been established that the algoflora is based on diatoms. Nine dominants have been identified. A comparison of the algoflora of the Tapsa River and the Khutinsky Nature Reserve is carried out. An ecological and geographical analysis of the algae of these watercourses is performed. It has been established that the algoflora of the rivers is represented by benthic species, with a predominance of indifferent forms in relation to the need and active reaction of the environment. A total of 137 types of saprobicity indicators are identified in all watercourses under study. The predominance of betamesosaprobionts and oligosaprobionts is noted. Geographically, cosmopolitan and boreal species dominated.</p>