Background : Natural ingredients have been used recently for its ability in curing various diseases and reducing the risk of antibiotic resistance . One of these natural ingredients is propolis. Bee propolis Geniotrigona thorasica from South Kalimantan has a strong antibacterial activity with active compounds such as flavonoids. Flavonoids can damage cell membranes and can fight the expansion of β-lactamase enzyme produced by gram-negative bacteria. Porphyromonas gingivalis is a gram-negative bacterium that causes chronic periodontitis with a prevalence of 80%. Objective : This study was to find out the inhibitory test of flavonoid propolis kelulut extract at the concentration of 0.1%; 0.3% and 0.5% on Porphyromonas gingivalis bacteria. Method : This type of research used a pure experimental method with post-test only and control group design. One-way ANOVA statistical test was performed with follow-up test of Post Hoc Dunnet’s T3 . Treatment was given to 4 groups with 5 repetitions. Observations were carried out using digital calipers in all groups after incubation for 24 hours with a temperature of 37℃. Results : One Way Anova and Post Hoc Dunnet's T3 showed significant differences in the diameter flavonoid propolis extract inhibitory zone against Porphyromonas gingivalis . The average value of Flavonoid extract inhibitory zone after 24 hours observation with a concentration of 0.5%; 0.3%; 0.1% and sterile distilled water were 25.24 mm; 18.04 mm; 13.58 mm and there was no inhibitory zone observed in sterile distilled water group . Conclusion : Extract of flavonoid propolis kelulut at the concentration of 0.1%; 0.3% and 0.5% can inhibit the growth of Porphyromonas gingivalis as an etiologic factor of chronic periodontitis.