Géneros de hongos: Icmadophila [13 taxones], Idiocercus [9 taxones], Idiomyces [1 taxon], Idriella [127 taxones], Ijuhya [7 taxones], Illosporium [19 taxones], Imimyces [2 taxones], Immotthia [3 taxones], Incrucipilum [5 taxones], Incrupila [6 taxones], Indiella [1 taxon], Inesiosporium [3 taxones], Inflatostereum [1 taxon], Infundibura [1 taxon], Ingoldiella [7 taxones], Inifatiella [5 taxones], Inocutis [3 taxones], Inocybe [178 taxones], Inocyclus [2 taxones], Inonotus [621 taxones], Inopilus [4 taxones], Insecticola [2 taxones], Intercalarispora [25 taxones], Iodophanus [316 taxones], Iodosphaeria [1 taxon], Ionomidotis [9 taxones], Ionophragmium [1 taxon], Irene [30 taxones], Irenina [3 taxones], Irenopsis [1058 taxones], Irpex [190 taxones], Irpiciporus [5 taxones], Irpicodon [7 taxones], Isaria [82 taxones], Isariopsis [44 taxones], Ischnoderma [49 taxones], Isia [2 taxones], Isipinga [20 taxones], Isoachlya [4 taxones], Isothea [7 taxones], Isthmiella [122 taxones], Isthmolongispora [10 taxones], Isthmophragmospora [1 taxon], Isthmospora [9 taxones], Isthmotricladia [7 taxones], Itajahya [9 taxones], Itersonilia [1 taxon], Ithyphallus [5 taxones], Iwilsoniella [1 taxon], Iyengarina [3 taxones]