One of the most common dental health problems is gingivitis, which is part of periodontal disease. Gingivitis is a periodontal disease caused by the accumulation of plaque bacteria in the form of Streptococcus mutans, Streptococcus sanguis, Actinomyces species, and Spirochaeta found on the tooth surface. Streptococcus mutans bacteria are Gram positive (+) bacteria that are facultative anaerobes and are relatively often found in the oral cavity, namely the tooth surface. Mouthwash can be interpreted as a solution with a comfortable taste, antimicrobial properties and can also freshen the mouth. Starfruit contains many active compounds and acts as an anti-microbial such as flavonoids, alkaloids, tannins, and saponins. Purpose: Proving the effectiveness of sunti starfruit extract (Averrhoa Blimbi L) as a mouthwash against gingivitis. Methods: The type of research used is a quasiexperimental research. The design used is a nonrandomized one group pretest-posttest. The population of the study was students of SMA Negeri 4 Semarang, with a total sample of 33 people. The sampling technique uses purposive sampling

Keywords : Gingivitis, Mouthwash extract sunti belimbing wuluh.