, Ialomitzia
, Ichthyochytrium
, Icmadophila
, Icmadophilaceae
, Idiocercus
, Idiomyces
, Idriella
, Igneocumulus
- Ijuhya antillana Lechat & Courtec., 2010
- Ijuhya aquifolii (Cooke & Ellis) Rossman & Samuels, 1999
- Ijuhya bambusina (Syd. & P. Syd.) Rossman & Samuels, 1999
- Ijuhya chilensis (Speg.) Rossman & Samuels, 1999
- Ijuhya dictyospora (Rossman) Rossman & Samuels, 1999
- Ijuhya equiseti-hyemalis Lechat & Baral, 2008
- Ijuhya fournieri Lechat, 2015
- Ijuhya hongkongensis J. Fröhl. & K.D. Hyde, 2000
- Ijuhya hubeiensis Y. Nong & W.Y. Zhuang, 2007
- Ijuhya leucocarpa (Samuels) Rossman & Samuels, 1999
- Ijuhya oenanthicola Lechat & Hairaud, 2012
- Ijuhya paraparilis (Samuels) Rossman & Samuels, 1999
- Ijuhya parilis (Syd.) Rossman & Samuels, 1999
- Ijuhya vitrea Starbäck, 1899
Fungi → Ascomycota → Sordariomycetes → Hypocreales → Bionectriaceae
, Iledon
, Ileodictyon
, Illosporiopsis
, Illosporium
, Ilyomyces
, Ilyonectria
, Ilytheomyces
, Imaia
, Imazekia
, Imicles
, Imimyces
, Immersaria
, Immersidiscosia
, Immersiella
, Immersisphaeria
, Immotthia
, Impudentia
- Imshaugia evernica (Elix & J. Johnst.) Elix
- Imshaugia pyxiniformis Elix
- Imshaugia sipmanii Elix
- Imshaugia subarida (Elix) Elix
- Imshaugia venezolana (Hale) Elix
Fungi → Ascomycota → Lecanoromycetes → Lecanorales → Parmeliaceae
, Incrucipulum
, Incrupila
, Incrupilella
, Incrustocalyptella
, Indiella
, Induratia
, Inermisia
, Inesiosporium
, Inflatispora
, Inflatostereum
, Infrafungus
, Infundibulicybe
, Infundibulomyces
, Infundibulum
, Infundibura
, Infundichalara
, Ingoldiella
, Ingoldiomyces
, Ingvariella
, Inifatiella
, Inocephalus
, Inocutis
, Inocybaceae
, Inocybe
, Inocyclus
, Inonotopsis
, Inonotus
, Insecticola
, Insiticia
, Insolibasidium
, Intercalarispora
, Intextomyces
, Intralichen
, Intrapes
, Involucropyrenium
, Involucroscypha
, Iodophanus
, Iodosphaeria
, Iodowynnea
, Ionaspis
, Ionomidotis
, Ionophragmium
, Iraniella
, Irene
, Irenina
, Irenopsis
, Iridinea
- Irpex africanus Van der Byl 1934
- Irpex alboluteus Rick 1959
- Irpex aridus (Svrcek) Kotir. & Saaren. 2002
- Irpex castaneus Lloyd 1920
- Irpex conchiformis (Sacc.) Kotir. & Saaren. 2002
- Irpex consors Berk. 1878
- Irpex cremicolor Miettinen, Niemelä & Ryvarden 2007
- Irpex destruens Petch 1909
- Irpex epitephrus Cleland 1936
- Irpex gracillimus Pilát 1925
- Irpex hacksungii J.S. Lee & Y.W. Lim 2009
- Irpex holoporus (Pers.) Sacc. & Traverso 1910
- Irpex hydnoides Y.W. Lim & H.S. Jung 2003
- Irpex irpicinus (Berk. & Broome) D.A. Reid 1963
- Irpex iyoensis Yasuda 1917
- Irpex javensis Lloyd 1925
- Irpex kusanoi Henn. & Shirai 1900
- Irpex lacteus (Fr.) Fr. 1828
- Irpex lamelliformis Lloyd 1917
- Irpex lepidocarpus (P. Karst.) Sacc. & Trotter 1912
- Irpex litschaueri (Bourdot & Galzin) Kotir. & Saaren. 2002
- Irpex longisporus Rick 1959
- Irpex longus Rick 1959
- Irpex merulioides (Berk. & Broome) Lloyd 1914
- Irpex microdon Rick 1959
- Irpex mikhnoi (P. Karst.) Sacc. & Trotter 1912
- Irpex miyabei Lloyd 1923
- Irpex mukhinii (Kotir. & Y.C. Dai) Kotir. & Saaren. 2002
- Irpex murashkinskyi (Burt) Kotir. & Saaren. 2002
- Irpex narymicus (Pilát) Saaren. & Kotir. 2002
- Irpex noharae (Murrill) Sacc. & Trotter 1912
- Irpex ochrosimilis Lloyd 1924
- Irpex owensii Lloyd 1916
- Irpex pallidus Lloyd 1920
- Irpex palmatus (Berk.) Speg. 1959
- Irpex poria Rick 1959
- Irpex rickii Lloyd 1925
- Irpex roseotingens (Hjortstam & Ryvarden) Saaren. & Kotir. 2002
- Irpex sepiarius Lloyd 1917
- Irpex subhypogaeus Rick 1932
- Irpex subrawakensis (Murrill) Saaren. & Kotir. 2002
- Irpex tasmanicus Syd. & P. Syd. 1903
- Irpex tiliaceus Pilát 1925
- Irpex tomentosocinctus Rick 1959
- Irpex unicolor Lloyd 1920
- Irpex vagus (Burds. & Nakasone) Saaren. & Kotir. 2002
- Irpex vellereus Berk. & Broome 1873
- Irpex versatilis Lloyd 1917
- Irpex woronowii Bres. 1920
Fungi → Basidiomycota → Agaricomycetes → Polyporales → Meruliaceae
- Irpicochaete nodulosa Rick 1940
Fungi → Basidiomycota → Agaricomycetes → Polyporales
- Irpicodon pendulus (Alb. & Schwein.) Pouzar 1966
Fungi → Basidiomycota → Agaricomycetes → Boletales → Amylocorticiaceae
- Irpicomyces cornicola T. Watan. 1994
- Irpicomyces schiffnerulae Deighton 1969
Fungi → Ascomycota
- Irydyonia filicis Racib. 1900
Fungi → Ascomycota → Leotiomycetes → Rhytismatales
, Isaria
, Isariella
, Isariopsis
, Ischnochaeta
, Ischnoderma
, Ischnostroma
, Ishwaromyces
, Isia
, Isipinga
, Isomucor
, Isomunkia
, Isothea
- Issatchenkia hanoiensis Thanh, Hai & Lachance, 2003 [1]
- Issatchenkia orientalis Kudryavtsev, 1960 [1]
Fungi → Ascomycota → Saccharomycetes → Saccharomycetales → Pichiaceae
, Isthmiella
, Isthmoconidium
, Isthmolongispora
, Isthmophragmospora
, Isthmospora
, Isthmosporella
, Isthmotricladia
, Itajahya
, Itersonilia
, Ithyphallus
, Ityorhoptrum
, Iwilsoniella
, Ixechinus
- Iyengarina asymmetrica Kuthub. & Nawawi, 1992
- Iyengarina elegans Subram., 1958
- Iyengarina furcata Kuthub. & Nawawi, 1992
Fungi → Ascomycota