The genus Elmis Latreille, 1802 belongs to the family of riffle beetles (Elmidae, Coleoptera). Elmidae are sensitive to environmental changes and are used as bioindicators of water quality, but their considerable morphological variability often makes standard species identification difficult. DNA barcoding is a method which enables rapid identification of species and detection of cryptic species via analysis of the sequence of mitochondrial gene for cytochrome oxidase, subunit I (COI). The main goal of this thesis is the identification and delimitation of species of the genus Elmis by DNA barcoding, for samples collected in the Western Palearctic area. Total genomic DNA was extracted from the samples, the COI gene was amplified and sequenced, phylogenetic trees were constructed, methods of molecular identification and species delimitation were performed, and separation time was estimated based on the molecular clock. Morphological identification has been confirmed for most samples, while a few samples probably belong to yet undescribed species. A total of 14 separate taxonomic units (MOTUs) were delimited, six of which represent new MOTUs for the BOLD database. The time-calibrated tree showed that most of the sister species separated in the period from the middle Pliocene to the early Pleistocene, while species groups separated in the Miocene. The results indicate the existence of as yet undescribed species as well as possible species complexes, and indicate the need for a detailed taxonomic revision of the genus Elmis.