Octospora, Genus
Oligoporus, Genus
Omphalina, Genus
Onnia, Genus
Onygena, Genus
Onygenaceae, Familia
Orbilia, Genus
Orbiliaceae, Familia
Orde Heliotiales, Ordo – synoniem of Leotiales, Ordo
Otidea, Genus
Oudemansiella, Genus
Oxyporus, Genus