Information on the nematodes of freshwater fishes of Japan published during 112 years between 1905 and 2016 is assembled as Parasite-Host and Host-Parasite lists. Fiffty-two nominal species and some unidentified species of the nematodes in 17 families, 3 orders, and 2 classes were reported during this period. The first part of this checklist includes 30 nominal species in the following nine families: Dioctophymatidae (1 species) in the order Dictophymatida, and Capillariidae (4 species) in the order Trichocephalida (class Dorylaimea); Anguillicolidae (2 species), Anisakidae (4 species), Camallanidae (2 species), Cucullanidae (3 species), Cystidicolidae (7 species), Daniconematidae (1 species), and Gnathostomatidae (6 species) in the order Spriruida (class Chromadorea). Information is also given on the nematodes of Acuariidae and other families that were not identified to species level.