Thelocarpon immersum is a species of lichen in the family Thelocarpaceae.

Found in Alaska, it was described as a new species in 2020 by lichenologist Alan Fryday.

The type specimen was collected in the Hoonah-Angoon Census Area of Glacier Bay National Park.

Here the lichen was found near the park entrance growing on soil in a calcareous wet meadow in a glacial outwash plain.

The specific epithet immersum refers to the perithecioid ascomata, which are immersed in "a mat of cyanobacteria and chlorococcoid algae, with only the tips protruding".