Introduction. Bats (Chiroptera) are the least studied group of mammals in many regions of Russia. At the same time, the chiropterans are known to be one of the largest orders of Mammalia, which can act as hosts and carriers of various pathogenic fungi, bacteria and viruses. However, the parasitic fauna of this group of animals is poorly investigated. The study of bat-parasitizing worms has great practical importance, since bats, due to their ancient origin, are a very detached order. Endoparasites, including the chiropteran helminths, have not been previously studied in the Rostov region. According to the available data, the up-to-date research on the bat parasites in Russia has been carried out only in the Saratov region and in the Republic of Mordovia. The aim of this series of articles is to study the helminth species composition parasitizing in chiropterans in the Rostov region. In the first report we present the data on nematodes.Materials and Methods. The materials for the research were the articles from the open access literature databases: PubMed (pubmed.ncbi.nlm.nih.gov), Cyberleninka (cyberleninka.ru), GoogleScholar (https://scholar.google.com ), etc. The main method used was the analysis of the collected data.Results. The authors were the first to reveal that 27 nematode species from 14 genera, 8 families, 4 orders and 2 classes can be found in 15 bat species living in the Rostov region. The numerous Chromadorea class is represented by 21 species, 12 of which are found in Russia.Discussion and Conclusion. The results of the literature sources analysis showed that the largest number of nematode species parasitize in two chiropteran species living in the Rostov region: in the Daubenton's bat (15 species) and in the common noctule (14 species). Only one species has been recorded in the northern bat. Most nematode species parasitize specifically in bats and have a direct life cycle. (e.g., species of the genus Molinostrongylus). For some species, such as Pterygodermatites bovieri and Litomosa spp., the intermediate hosts are arthropods and the definitive hosts are various bat species. For three nematode species: Ascarops strongylina, Physocephalus sexalatus and Spirocerca lupi, bats are the paratenic hosts.