The western border region of Hungary, including Kőszeg and its surroundings, is a poorly documented region from an algal point of view. The first reason for this is that the major standing water bodies found here are all artificial and relatively young in age. However, in the absence of other natural water bodies, they are important as potential wetland habitats, as is the information needed to conserve them. The present paper is the first to describe the algal flora of Téglagyári-tó in Kőszeg in the context of the planned process of processing lakes and reservoirs in the area. Despite its small size and the distur­bance caused by its recreational use, Téglagyári-tó is a species-rich, highly diverse habitat in terms of algal diversity. The Chlorophyta division accounts for the majority of the species recorded, but the Charopyta, Euglenophyta and Heterocontophyta divisions also make a significant contribution. Its value is particu­larly enhanced by rare species (e.g. Stauridium privum, Cosmarium sinostegos var. obtusius), not to ment­ion the red-listed endangered species (Cosmarium anceps, Cylindrocystis brebissonii, Euastrum bidentatum, Euastrum denticulatum, Penium spirostriolatum, Staurastrum oxyacanthum, Staurastrum tetracerum). A special feature is the presence of desmids (Euastrum biverrucosum, Euastrum minimum, Staurastrum levanderi var. hollandicum), which are not yet recorded in the region, and which colonise the slightly alka­line mesotrophic environment of the lake, otherwise known from a more acidic eutrophic environment. As a curiosity, Entomoneis ornata should be mentioned, which was identified in an environment associa­ted with higher salinity waters and only moderately loaded with inorganic nutrients.