The reproductive system of the mature male and female viviparid snail, Bellamya unicolor (Olivier, 1804) was studied by gross dissection and histological examination and a reference to the function of each part was made. External differences between male and female were found in the relative size and the form of the right tentacle. The male genital organs consist of the well developed testis lying in the mantle cavity, characteristic of genus Bellamya, the thin proximal vas deferens, the prostate gland and the distal vas deferens extending within the right tentacle and opening at its tip. The female genital organs are composed of a remarkably small ovary, a thin oviduct, a U-shaped glandular and thick oviduct, an albumen gland, a glandular inverted U-shaped receptaculum seminis, a brood pouch and a vagina. The brood pouch is adapted for the incubation of the eggs till after hatching. The young snails emerge from the female genital opening singly. A gonopericardial duct was ob served only in the female. The results of this study were discussed in comparison with those of other mesogastropods especially those belonging to the family Viviparidae.