Postia cylindrica is a species of poroid fungus in the family Fomitopsidaceae.

The type collection was found growing on a dead pine tree in Jiangxi.

The fungus is characterized macroscopically by crust-like to effused-reflexed fruit bodies with a cream to buff coloured cap surface and a reddish-brown margin that curves inward.

There are gloeoplerous (oily) hyphal cells in the cuticular layer, and an absence of cystidia in the hymenium.

The fungus produces smooth, cylindrical, thin-walled spores measuring 4.7–5.2 by 1.3–1.5 μm.