Postia is a genus of brown rot fungi in the family Fomitopsidaceae.

Postia was circumscribed by mycologist Elias Magnus Fries in his 1874 work Hymenomycetes europaei.

[2] The genus name honours Swedish naturalist Hampus von Post (1822–1911).

[3] A 2008 estimate placed 30 species in the genus.

[4] As of June 2018[update], Index Fungorum accepts 57 species of Postia:[5] In a 2018 revision of the Postia caesia complex, Otto Miettinen and colleagues proposed four new combinations, and described ten new species:[19]