Information on the protistan and metazoan parasites of four species of eels (the Japanese eel Anguilla japonica, the giant mottled eel Anguilla marmorata, the European eel Anguilla anguilla, and the short-finned eel Anguilla australis) in Japan is summarized in the Parasite-Host and Host-Parasite lists, based on the literature published for 103 years between 1915 and 2017. This is a revised and updated version of the checklist published in 2007. Anguilla japonica and A. marmorata are native to Japan, whereas A. anguilla and A. australis are introduced species from Europe and Australia, respectively. The parasites, including 54 nominal species and those not identified to species level, are listed by higher taxa as follows: Sarcomastigophora (no. of nominal species: 0), Ciliophora (6), Microspora (1), Myxozoa (6), Trematoda (12), Monogenea (8), Cestoda (3), Nematoda (7), Acanthocephala (6), Hirudinida (3), Bivalvia (1), and Copepoda (1). For each parasite species listed, the following information is given: its currently recognized scientific name, any original combination, synonym(s), or other previous identification used for the parasite from Japanese eels; habitat (freshwater, brackish, or marine); site(s) of infection within or on the host; known geographical distribution in Japanese waters; and the published source of each locality record. Of the 54 nominal species of parasites listed, 50 are from A. japonica, six from A. marmorata, nine from A. anguilla, and one from A. australis. Five species, viz., Gyrodactylus anguillae, Gyrodactylus nipponensis, Pseudodactylogyrus mundayi (Monogenea), Bothriocephalus claviceps (Cestoda), and Raphidascaris acus (Nematoda), have been regarded as introduced parasites from other countries, and the remaining 49 nominal species are indigenous parasites of Japan. Nine nominal species of marine and/or brackish-water origin, viz., Lecithochrium musculus, Proctotrematoides pisodontophidis, Tubulovesicula anguillae (Trematoda), Gyrodactylus nipponensis, Pseudodactylogyrus kamegaii (Monogenea), Nybelinia angullicola (Cestoda), Cucullanus filiformis, Heliconema anguillae (Nematoda), and Limnotrachelobdella okae (Hirudinida), have been reported from A. japonica. Individiduals of A. japonica known as “sea eels” and “estuarine eels” inhabiting coastal marine and riverine brackish waters are considered to serve as hosts for those marine and/or brackish-water parasites.