During the revision of the Neotropical Fomitiporia species, a collection from French Guiana was found to represent an undescribed species, on the basis of both morphological and molecular (DNA sequence) data. This taxon is described and illustrated as Fomitiporia expansa sp. nov. It is characterized by widely effused basidiomata, extending over 1 m long, with a variable greyish to light brownish grey pore surface, and microscopically in having basidiospores averaging 6.0 × 5.5 µm. It is known for the time being from a single specimen originating in the western edge of French Guiana, in rainforest. The species belongs to the Fomitiporia langloisii lineage. This lineage contains for the time being species with resupinate basidiomata spanning over the Neotropics.