<p><strong><em>Introduction: </em></strong><em>The cause of respiratory tract infection (ARI) taken from sputum material, the average result is Klebsiella pneumoniae bacteria. Infection caused by the bacterium Klebsiella pneumoniae is the third cause of death after cardiovascular disease and tuberculosis. <strong>The purpose of this study: </strong>was to determine the inhibition of the ethanol extract of basil leaves (Ocimum sanctum linn) on the growth of Klebsiella pneumoniae bacteria. <strong>This research method</strong>: is descriptive analytic. The population used was Klebsiella pneumoniae isolates obtained from Jombang Hospital. The sample in this study was a suspension of Klebsiella pneumoniae bacteria. The sampling technique in this study was simple random sampling. The test method used is disc diffusion. <strong>The results:</strong> of the phytochemical test results of the ethanol extract of basil leaves (Ocimum sanctum linn) were positive for Alkaloids, Flavonoids and Tannins. The diameter of the inhibition zone at a concentration of 100% is 3.8 mm, the diameter of the inhibition zone at a concentration of 75% is 2.3 mm, the diameter of the inhibition zone at a concentration of 50% is 2.3 mm, and the inhibition zone at a concentration of 25% is 0.3 mm. This is because of the different concentrations and the content of secondary metabolites at each concentration is also different. <strong>The conclusion:</strong> of the ethanol extract of basil leaves (Ocimum sanctum linn) on the growth of Klebsiella pneumoniae bacteria is in the weak category</em></p>