Abstract: A new species of Balantidium is described in this paper. The body is somewhate obovoid in shape, almost rounded in cross section. The posterior end is narrower than the anterior extremity. The peristome which appears as a rift-like groove in live material, and elliptical in Protargol stained material with a row of dense cilia on the left margin, becomes deeper and narrower as it sinks backward forming a cytostome. There are three contractile vacuoles, two of them are close to the sides near the middle part and another one is situated near the posterior region of the body. The micronucleas usually lies on the middle part of the macronucleus which is long elliptical. Body measured from 99.2136.4m in length and 47.7276.88m in width. The macronucleus is 25.032.24m in length and 7.4414.88m in breadth. These characteres differ from all the species hitherto described in the genus and the name Balantidium fulinensis sp. nov. is here proposed. Observations from both live material and fixed sections of B. fulinensis sp. nov. revealed that is ciliate only caused some local necroses or ulcers through mechanical actions. Thus, this ciliate may not bring about serious damage to the intestinal tissue of the fish.