Mouthwash is a preparation in liquid form and contains antibacterial substances. Neem leaves contain a class of compounds in the form of steroids/triterpenoids which are useful for antibacterial activity so they have the potential to be used as active substances in mouthwash preparations. The aim of this research was to determine the effect of variations in glycerin concentration on the physical quality and stability of neem leaf extract (Azadirachta indica A. Juss) mouthwash preparations. To determine the antibacterial effect and formula for mouthwash from neem leaf extract which has the most effective antibacterial effect against the bacteria Streptococcus mutans. This research uses four formulations for mouthwash from neem leaf extract (Azadirachta indica A. Juss) at 1% with variations in glycerin concentration of F1 (12%), F2 (24%), F3 (30%). Physical quality testing of the preparation includes organoleptic, homogeneity, specific gravity, pH, viscosity and stability of the preparation (cycling test). Mouthwash preparations were tested against Streptococcus mutans bacteria using the paper disc diffusion method. The research results showed that mouthwash preparations in all formulas with organoplastic physical quality, homogeneity, viscosity, pH, specific gravity and stability produced good preparations. In testing the antibacterial activity of mouthwash preparations, the diameter of the inhibition zone was obtained, namely F1 9.94 mm; F2 11.57mm; F3 8.91mm; F- (k-) 0 mm; and positive control 9.47 mm. From the third formula, the one with the best inhibition zone diameter is F2. AbstrakObat kumur merupakan sediaan yang berbentuk cairan dan memiliki kandungan zat antibakteri. Daun mimba memiliki kandungan golongan senyawa berupa steroid/triterpenoid yang bermanfaat sebagai aktivitas antibakteri sehingga berpotensi untuk dijadika zat aktif pada sediaan obat kumur. Tujuan dari penelitian ini untuk mengetahui pengaruh variasi konsentrasi gliserin terhadap mutu fisik dan stabilitas sediaan obat kumur ekstrak daun mimba (Azadirachta indica A. Juss). Mengetahui efek antibakteri dan formula obat kumur ekstrak daun mimba yang paling efektif efek antibateri terhadap bakteri Streptococcus mutans.Penelitian ini menggunakan empat formula sediaan obat kumur ekstrak daun mimba (Azadirachta indica A. Juss) sebesar 1% dengan variasi konsentrasi gliserin sebesar F1 (12%), F2 (24%), F3 (30%).Pengujian mutu fisik sediaan meliputi organoleptis, homogenitas, berat jenis, pH, viskositas, dan stabilitas sediaan (cycling test). Sediaan obat kumur diujikan terhadap bakteri Streptococcus mutans menggunakan metode difusi cakram kertas. Hasil penelitian menunjukkan bahwa sediaan obat kumur pada semua formula dengan mutu fisik organoplik, homogenitas, viskositas, pH, berat jenis dan stabilitas menghasilkan sediaan yang baik. Pada pengujian aktivitas antibakteri sediaan obat kumur didapatkan nilai diameter zona hambat yaitu F1 9,94 mm; F2 11,57 mm; F3 8,91 mm; F- (k-) 0 mm; dan kontrol positif 9,47 mm. Dari ketiga formula yang memiliki diameter zona hambat paling baik yaitu F2.