The purpose of the research is to study biodiversity of gastrointestinal strongylates in sheep grazing on pastures of different ecological types in lowland Dagestan.Materials and methods. In 2004–2020, biodiversity was studied of gastrointestinal strongylates in sheep on lowland wet, steppe, saline, semi-desert, and shrub pastures in lowland Dagestan. In total, 360 collections of gastrointestinal tract were dissected and 500 fecal samples from sheep were examined. The studies were performed in all seasons by age groups: lambs, young animals from one to two years old and sheep from three years old and older. The work used methods of complete helminthological dissection according to K. I. Skrjabin, sequential washing, flotation with a saturated ammonium nitrate solution according to G. A. Kotelnikov and V. M. Khrenov, and larvae cultivation in a thermostat.Results and discussion. The biodiversity of gastrointestinal strongylates in sheep in lowland Dagestan was represented by 31 species, including the genus Chabertia, 1 species, 2 genus Bunostomum species, 3 genus Oesophagostomum species, 5 genus Trichostrongylus species, 6 genus Ostertagia species, 1 genus Maramastrongylus species, 2 genus Marschallagia species, 1 genus Haemonchus species, 3 genus Cooperia species, and 7 genus Nematodirus species. The Strongylata prevalence (the IP) in sheep was 100% with the infection intensity (the II) of 1–3860 parasites. The prevalence of infection with individual species varied as follows: 1.6% with M. schikobalovi, 44.1% with B. trigonocephalum with the II of 1 specimen of O. columbianum and 3860 specimens of H. contortus. The biodiversity was dominated by Ch. ovina, B. trigonocephalum, T. axei, T. capricola, T. colubriformis, T. skrjabini, T. vitrinus, H. contortus, N. filicollis, N. helvetianus and N. spathiger in terms of the prevalence. The IP of 1.6–10.0% and the II of 1–23 specimens were recorded in B. phlebotomum, and in species Oesophagostomum, Ostertagia, Maramastrongylus, Marschallagia, Cooperia, N. oiratianus, N. abnormalis, N. dogeli and N. andreevi. Rich species diversity and high rates of the prevalence (17.5–44.1%) and intensity of infection (1–3860 specimens) were observed in strongylates on lowland wet and plain steppe pastures.