>Diarrhea is a health problem that occurs throughout the world, in Indonesia the prevalence of diarrhea is 11%. Diarrhea is one of the food borne diseases. The most common bacteria that causes diarrhea is Escherichia coli. Diarrhea can be prevented by disinfection using 70% alcohol hand sanitizer, but this material often causes irritation and itching, so alternative materials were needed. One of the potential ingredients is eucalyptus oil (Melaleuca leucadendra) made in Lamongan, because it contains 1,8-Cineol compounds. This study aimed to analyze the antibacterial potential of eucalyptus oil as a solution to health problems. This study was a true experimental study with a posttest-only control group design. Sampling used a simple random sampling technique. Data were obtained by measuring the diameter of the inhibition zone using the diffusion method antibacterial test. The data would be processed using IBM SPSS Statistics 23 software. The results of the measurement of the diameter of the inhibition zone in positive control (31.53 ± 0.6 mm), negative control (0.00 ± 0.00 mm) 20% concentration (19.00 ± 1.17 mm), 30% concentration (21.53 ± 1.33 mm), 40% concentration (24.08 ± 0.28 mm), and 50% concentration (24.76 ± 1.56 mm). Based on the One-Way ANOVA test, it was found that there was a significant difference between the control group and the treatment group (p = 0.000). Based on the Pearson test, it was found that there was a very strong relationship (r = 0.888), positive (r = 0.888) and significant (p = 0.000) between various concentrations of eucalyptus oil (Melaleuca leucadendra) made in Lamongan against Escherichia coli bacteria. There was a significant antibacterial effect of eucalyptus oil (Melaleuca leucadendra) made in Lamongan against Escherichia coli bacteria.