Guava leaves (Psidium guajava L.) thrives in the eastern part of Indonesia, one of which is Papua. Guava leaves (Psidium guajava L.) can also be used as an antibacterial, one of which is guava leaves which contain chemical alkaloids, tanins, which have antibacterial effectiveness. The purpose of this study was to determine the antibacterial activity of guava leaves (Psidium guajava L.) at concentrations of 25%, 50%, and 75% against the growth of Escherichia coli bacteria. This research is a laboratory experimental study using the infusion method with aquadest as a solvent. This study used the disc method with Ciprofloxacin as a positive control and aquadest as a negative control. The results showed that all concentrations of guava leaf infusion had an inhibition zone diameter of Escherichia coli bacteria with an average diameter of inhibition formed by infusion with a concentration of 25% having an inhibition zone diameter of 10.94 mm, 50% diameter 11.54 mm, concentration of 75% the diameter is 12.39 mm. The presence of an inhibition zone that occurs in Escherichia coli bacteria proves that guava leaves contain active compounds that have antibacterial properties. In this study it can be concluded that there is antibacterial activity of guava leaf infusion (Psidium guajava L.) against Escherichia coli bacteria at concentrations of 25%, 50% and 75% with weak inhibition zone categories.