Project description:Simple Summary As the most diverse genus in the family Limnephilidae, Limnephilus Leach, 1815 (194 extant species and 9 fossil species), has a wide distribution and a broad range of ecological tolerances among its species. Although it has a high species diversity in the Holarctic region, only 16 species have been recognized in China until now, of which 7 are endemic to China. In this study, a new species of the genus Limnephilus was found. The adult females, larvae, and pupae of this new species were associated with the adult males based on COI sequencing, and all the life stages except for the egg stage are described and illustrated. In addition, the biological and habitat information for this new species is provided. Furthermore, all of the Limnephilus species from the Chinese mainland are revised at the species group level, and diagnoses for species groups and species (keys of groups and species) are given, along with a distribution map. Abstract Fifty individuals of Limnephilus from the Qinghai Province, China, were examined, and their COI barcode sequences were extracted and analyzed. Forty individuals of Limnephilus from the Insect Collection of Nanjing Agricultural University (ICNAU), China, were examined, and photos of the male genitalia of four Limnephilus species are here presented. The males, females, larvae, and pupae of a new species, Limnephilus deqianensis n. sp., associated via COI barcode sequences, are described and illustrated. Ecological photos of the male, pupal case, and the habitat of the new species L. deqianensis n. sp. are also provided. Five species groups containing all seventeen Chinese Limnephilus species are revised. Diagnoses, keys, and a distribution map of them are provided. All of the sequences have been uploaded to GenBank. All specimens are deposited in the ICNAU, Nanjing, Jiangsu Province, P. R. China.