Atrichum tenellum, also known as the slender smoothcap,[1] is a species of moss belonging to the family Polytrichaceae.

[2] It is red listed in Iceland as a critically endangered (CR) species.

[1] A. tenellum is an uncommon species, which can be found in a range of disturbed, acidic and open habitats.

This species can be found growing in woodland habitats where it inhabits rides, but also in ditches and even open heathlands and grasslands.

Populations can also be found on the banks of streams, lakes and reservoirs where the soil is moist.