Macrolepiota gracilenta – synoniem of Macrolepiota mastoidea
Macrolepiota rhacodes – synoniem of Macrolepiota rachodes
Melanoleuca melaleuca – synoniem of Melanoleuca polioleuca
Melanophyllum echinatum – synoniem of Melanophyllum haematospermum
Melanotus caricicola – synoniem of Psilocybe caricicola
Melanotus horizontalis – synoniem of Psilocybe horizontalis
Merismodes anomalus – synoniem of Merismodes anomala
Mitrophora semilibera – synoniem of Morchella semilibera
Mniopetalum globisporum – synoniem of Rimbachia arachnoidea
Monilia fructigena – synoniem of Sclerotinia fructigena
Monilinia fructigena – synoniem of Sclerotinia fructigena
Mycena galopus var. alba – synoniem of Mycena galopus
Mycena leucogala – synoniem of Mycena galopus
Mycena oortiana – synoniem of Mycena arcangeliana
Mycolachnea hemisphaerica – synoniem of Humaria hemisphaerica
Myxarium hyalinum – synoniem of Myxarium nucleatum