Abstract The ectosymbiont fauna associated with crustaceans in South American inland waters is characterized by a marked microendemism, as the species concerned appear to show high host specificity. The aim of the present study is to present a review of ciliated Protozoa reported as ectosymbionts on South American inland water malacostracans. The literature revealed the existence of three genera, Chilenophrys with one species, Lagenophrys with five species, and Operculigera with seven species. The main limiting factor is that many species descriptions require further validation, as the reports have not been confirmed. The literature reports the presence of Lagenophrys lenticulata associated with Hyalella curvispina from Uruguay. H. curvispina is widespread throughout southern South America, including Argentina and Chile, and it may be possible to find epibionts on other populations of H. curvispina , as well as on other Hyalella populations. Lagenophrys aegleae has been recorded on the genus Aegla in eastern and western South America; L. antichos on crayfishes in east and west South America; and L. lenticulata on amphipods in North America and Uruguay. Ecological and biogeographical topics are also addressed.