Introduction. Infectious diseases and cancer remain among the leading causes of death worldwide. In this regard, the search for biologically active molecules from among synthetic and natural compounds for the purpose of creating medicines remains an urgent task of modern science. Plants that have impressive natural and biotechnological resource potential, taking into account modern advances in the field of ex situ, in situ and in vitro cultiva-tion, remain a promising source of native substances. One of the promising sources of biologically active substances is a perennial plant, the Seseli libanotis (L.) W.D.J. Koch, Apiaceae, growing in central, eastern Europe and Asia in dry pastures and forest edges. The main components of the genus Seseli L. are furo- and pyranocoumarins, essential oils and polyacetylene compounds, which exhibit antibacterial, antifungal, insecticidal, diuretic, antiviral, anti-inflammatory, and antitumor properties. The aim – study of the chemical composition, antibacterial and cytotoxic activities of S. libanotis roots essential oil. Material and methods. The roots were collected in places of natural growth in September 2022, during the fruiting period (Irkutsk region, Maloye Goloustnoye village). The voucher specimen is stored in the herbarium of the Institute of Ecological Ecology SB RAS (UUH 020438). Obtaining essential oils. Essential oils were obtained by hydrodistillation. The qualitative composition and quantitative content of essential oil compo-nents were studied by GC/MS. The study of the antibacterial activity of essential oils was carried out in vitro on test cultures of gram-positive and gram-negative bacteria (Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli, Pseudomona saeruginosa, Salmonella enterica) using the disc diffusion method. Cell viability assay was performed on HeLa cell lines using trypan blue. Results. The composition and quantitative content of the components of essential oils of the roots of S. libanotis of the Baikal flora were studied for the first time. 28 components of predominantly monoterpene nature have been identified, the main ones being limonene (57,60%), α-pinene (6,88%), cis-β-ocimene (6,75%). Also found were fatty acids, polyacetylene-falcorinol and 7-isopen-tinyloxycoumarin. Essential oils of S libanotis have antibacterial activity against gram-positive bacteria Staphylococcus aureus, Streptococcus pyogenes and gram-negative bacteria Escherichia coli. Cultivation of Hela with S. libanotis essential oils resulted in decreased viability in the concentration range of 0.04–2.56 μL/mL for 72 hours. Conclusions. Essential oils of roots of S. libanotis, with high yield, containing falcarinol and coumarin, have antibacterial and cytotoxic activity.