There are 68 known species of Hyalella worldwide, with 23 occurring in Brazil. The state of Rio Grande do Sul, Southern Brazil, has the largest diversity of the genus in the country, with nine species recorded. The current study aimed to describe two new species of Hyalella from state of Rio Grande do Sul, both of them in the Northwest region of the state, one found in a small spring and another in an artificial pond. Hyalella georginae n. sp. presents several clusters of simple setae on antenna 2, maxilliped very slender, gnathopod 2 dactylus not reaching the lobe of propodus, pleopods rami with short plumose setae and a peculiar pattern of setae on uropods and telson. Hyalella gauchensis n. sp. presents antenna 2 with few setae, maxilliped very slender, gnathopod 2 dactylus reaching the lobe of propodus and pleopods rami with long plumose setae. From this work, the number of Hyalella species found in Brazil increases to 25 and 70 for the genus.
Keywords: Crustacea, freshwater crustaceans, diversity, Peracarida, South America, taxonomy.