Leucocoprinus thoenii is a species of mushroom producing fungus in the family Agaricaceae.

[3][4] Heinemann notes that this species may be the same as Lepiota elongata which the Belgian mycologist Maurice Beeli had annotated an illustration with but never formally classified.

Heinemann provided only a basic description of the features species based on a dried specimen provided by D. Thoen[6] and an observation logged with the Meise Botanic Garden by M. Goossens-Fontana in 1939 which Beeli had annotated with a suggested name.

GBIF records only two observations of this species in the Democratic Republic of the Congo with one at Binga in 1939 and the other at Kipopo in 1973.

A 1982 study conducted at the University of Michigan by the mycologists Helen Vandervort Smith and Nancy S. Weber noted that L. thoenii is similar to Leucocoprinus magnicystidosus and Leucocoprinus fragilissimus but has larger spores and differences in cellular features.