This work was inspired by the growing international interest in the study of natural products of plant origin with bioactive properties that can replace synthetic chemical pesticides in the control of pathogens. The aim of this study was to explore the in vitro activity of Lanvandula dentata L. essential oil (EO) on Fusarium oxysporum f. sp. radicis-lycopersici (FORL), a dangerous fungal plant pathogen, causal agent of tomato crown and root rot. Initially, we proceeded to identify the forma specialis of two strains of F. oxysporum by PCR based on the differences in the genes responsible for the synthesis of endo-polygalacturonases (pg1) and exo-polygalacturonases (pgx4) and then tested the activity of the EO on these strains by the direct contact method at different concentrations. The results showed that increasing the concentration of EO had a significant inhibitory effect, with a minimum inhibition rate of 49.3±2.2 % and 21.8±4.2 for the strains IB19501 and IB19502 respectively at the 0.25 μL/mL concentration and reaching 100±0.0 at the 1 μL/mL concentration for both strains. The data of this study reveal an important anti-fungal activity of the EO of L. dentata, these effects further validate the interest of our study and the traditional use of this plant, while indicating the possibilities of its potential use as a natural alternative to pesticides for the control of pathogenic fungi and thus preserve human health and the environment.