AbstrakAdanya penurunan populasi ikan tambakan betina saat ini diperlukan upaya untuk mendukung keberlangsungan hidup ikan tambakan melalui teknik feminisasi. Feminisasi dapat dilakukan dengan memanfaatkan ekstrak daun kemangi (Ocimum sanctum L) karena mengandung fitoestrogen alami. Penelitian dilakukan selama 3 bulan di Workshop Pembenihan Ikan Fakultas Perikanan dan Kelautan Universitas PGRI Palembang dan Laboratorium Biologi Fakultas Sains dan Teknologi Universitas PGRI Palembang. Penelitian menggunakan metode Rancangan Acak Lengkap dengan 6 taraf perlakuan dan 3 ulangan dengan perlakuan 0,5, 10, 20, 40, dan 80 mg/L. Penelitian ini diperoleh hasil perendaman ikan tambakan pada ekstrak kemangi menghasilkan persentase betina tertinggi pada perlakuan P4 (40mg/L) sebesar 85%. Pertambahan bobot ikan tambakan yang optimal diperoleh pada perlakuan P4 sebesar 0,66 g, pertambahan panjang yang optimal diperoleh pada perlakuan P4 sebesar 2,37 cm, sedangkan kelangsungan hidup ikan tambakan tertinggi yang dipelihara selama 30 hari pada perlakuan P4 sebesar 96,66%, dapat disimpulkan perlakuan P4 memberikan efek yang signifikan dalam setiap parameter pengamatan.AbstractThe decline in the population of female kissing gouramy is currently needed efforts to support pursued to support the survival kissing gouramy fish through feminization techniques. Feminization can be done by utilizing extracts from basil leaves (Ocimum sanctum L) because they contain natural phytoestogens. The research was conducted for 3 months at the Fish Hatchery Workshop of the Faculty of Fisheries and Marine, PGRI Palembang University and the Biology Laboratory of the Faculty of Science and Technology, PGRI Palembang University. The study used the Complete Random Design method with 6 treatment levels and 3 repeats with treatments of 0.5, 10, 20, 40, and 80 mg/L. From this study obtained the results of soaking kissing gouramy fish in basil extract result in the highest percentage of females at P4 treatment (40mg/L) which is 85%. The optimal weight gain of kissing gouramy fish is obtained at the P4 treatment of 0.66 g, the optimal length gain is obtained at the P4 treatment of 2.37 cm, while the survival of the highest kissing gouramy maintained for 30 days at P4 treatment was 96.66%, it can be concluded that the P4 treatment gives a significant effect in each observation parameter.