Abstract. Rokhmani, Riwidiharso E, Darsono, Utami P. 2018. Morphological variations, prevalence and intensity of Trichodina spp. on fish in the Kranji River Purwokerto, Central Java. Pros Sem Nas Masy Biodiv Indon 5: 312-315. Trichodina spp. is a pathogenic ectoparasite protozoa from the ciliate group that usually attacks freshwater and marine fish. The disadvantage of this ectoparasitic infection is not great, but the infection can be a predisposing factor for infection with secondary pathogens that are more dangerous. This protozoan life is ubiquitous (cosmopolitan) and as obligate parasites in the aquatic environment. Research has been conducted to find out what species, and the prevalence of Trichodina sp. in catched fish in the Kranji river, Purwokerto, Central Java. This research method is a survey by taking a sampling location on the Kranji River in Purwokerto City. Fish retrieval by netting and analyzing randomly at the research location. The results of the research on species found in catched fish in the Purwokerto Kranji river are Trichodina nobilis, Trichodina acuta, Trichodina heterodentata, Trichodina magna, Trichodina pediculus, and Trichodina nigra. The prevalence of the event was 48%, and the intensity was 21.3 individuals/head.