ABSTRAK Karies gigi merupakan penyakit dengan prevalensi tinggi di Indonesia yang disebabkan oleh bakteri Streptococcus mutans. Daun sirsak (Annona muricata Linn) merupakan salah satu tanaman berkhasiat obat yang dapat menghilangkan plak pada gigi. Penelitian ini bertujuan untuk menentukan kandungan kimia dan mengukur daya hambat antibakteri ekstrak metanol daun sirsak dalam menghambat pertumbuhan bakteri Streptococcus mutans. Penapisan fitokimia menyatakan bahwa daun sirsak mengandung senyawa flavonoid, alkaloid, tanin, steroid, glikosida dan saponin. Uji daya hambat diukur menggunakan metode difusi kertas cakram dengan variasi konsentrasi yaitu 5, 10, 15 20, dan 25%, kontrol positif tetrasilkin 30 µg dan kontrol negatif pelarut metanol. Hasil pengujian antibakteri menunjukkan bahwa ekstrak metanol daun sirsak memiliki aktivitas antibakteri terhadap Streptococcus mutans pada konsentrasi 5, 10, 15, 20 dan 25% dengan masing-masing diameter hambat sebesar 9,1; 10,57; 11,53; 12,01 dan 13,75 mm. Kata kunci: Daun Sirsak, Streptococcus mutans, Metanol. ABSTRACT Dental caries is a disease with a high prevalence of caries in Indonesia is caused by the bacterium Streptococcus mutans. The leaves of the soursop (Annona muricata Linn) is one of the herbs that can remove dental plaque. This study aims to determine the chemical content and measure the inhibitory antibacterial soursop leaf methanol extract in inhibiting the growth of Streptococcus mutans bacteria. Phytochemical screening stated that the leaf of the soursop contains flavonoids, alkaloids, tannins, steroids, glycosides and saponins. Test of inhibition were measured using paper disc diffusion method with variation concentrations of 5, 10, 15 20, and 25%, positive control is tetrasilkin 30 µg, and a negative control is methanol. Antibacterial test results showed that the methanol extract of soursop leaves have antibacterial activity against Streptococcus mutans at concentrations of 5, 10, 15, 20 and 25% with inhibitory diameter of 9.1; 10.57; 11.53; 12.01 and 13.75 mm respectively. Keywords: Soursop leave, Streptococcus mutans, Methanol.