Leptogium compactum is a species of corticolous (bark-dwelling), foliose lichen in the family Collemataceae.

[1] Found in northwestern North America, it was formally described as a new species in 2016 by Daphne Stone, Frances Anderson, and James Hinds.

[2] The internal anatomy of this lichen shows a tightly packed, interwoven thallus, with long, undulating hyphae that run more or less parallel to cortices.

The Nostoc photobiont appears as single cells or short chains between the compactly packed hyphae.

The upper and lower cortices consist of a single (rarely double) layer of almost isodiametric cells.

The disc is reddish-brown and flat, with the outer part of the apothecial margin concolorous with the thallus and becoming covered with isidia (0.1–0.2 mm wide).