Abstract:Marine turtle leeches (Ozobranchus spp.) are ectoparasites of sea turtles. Only 2 species were identified on turtles examined from near Taiwan: Ozobranchus branchiatus, with 7 pairs of external gills on each side of its abdomen and only found on the green sea turtle (Chelonia mydas); and Ozobranchus margoi, with 5 pairs of external gills on each side of its abdomen. We report the first records of both leech species from Taiwan. We observed approximately 400 O. margoi on a loggerhead turtle (Caretta caretta) taken as by-catch in the pond-net fishery on December 14, 2009.