en Anti-microbial agents, resistance and treatment protocols Anti-microbial agents, resistance and treatment protocols Original article Original article <strong>Introduction:</strong> Plant essential oils can be used as alternative agents for the treatment of antibiotic-resistant pathogenic bacteria. This study aimed to investigate the chemical composition, antibacterial, and antioxidant activity of <em>Thymus eriocalyx </em>and<em> Thymus daenensis</em> essential oils against Gram-positive and Gram-negative human pathogenic bacteria. <strong>Methods:</strong> The aerial part of <em>Thymus eriocalyx </em>and <em>Thymus daenensis </em>in the full flowering stage were collected from West Azerbaijan Province (Urmia), Iran, in 2014. We obtained the essential oils using a Clevenger device. The disc diffusion method was used to determine the antibacterial activity of the essential oils against 15 Gram-positive and Gram-negative PTCC and ATCC bacterial standards. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were measured by microdilution broth method in 96-well plate and free radical scavenging activity by 2,2-diphenyl-1-picrylhydrazyl. Chemical analysis of the essential oils performed out by gas chromatography connected to Mass spectrometry. <strong>Results:</strong> Eleven (94.06%) and seven (90.76%) compounds were identified in <em>T. eriocalyx </em>and <em>T. daenensis </em>essential oils, respectively. The major components of <em>T. eriocalyx </em>essential oil were thymol (37.8%) and &alpha;-terpineol (14.91%), and of <em>T. daenensis</em> were thymol (52.36%) and carvacrol (16.72%). <em>T. eriocalyx</em> essential oil showed the highest activity against <em>B. cereus </em>with MIC of 0.93 &mu;g mL^-and MBC of 1.87 &mu;g mL^-. The most potent radical scavenging activity was also obtained for <em>T. daenensis</em> essential oil<span dir="RTL">. </span><strong>Conclusion:</strong>&nbsp; Essential oil components of <em>T. eriocalyx </em>and <em>T. daenensis </em>may have the potential to be used as antimicrobial agents against antibiotic-resistant pathogenic bacteria.&nbsp; Essential oil, Antibacterial, Chemical composition, Pathogenic bacteria, Thymus spp 148 154 http://jommid.pasteur.ac.ir/browse.php?a_code=A-10-253-1&slc_lang=en&sid=1 mostafa alamholo mostafaalamholo@yahoo.com 0000-0003-1644-8179 Yes Bu Ali Sina University