Polysiphonia devoniensis is a species of marine algae.

It is a small red alga in the Division Rhodophyta.

[1] Polysiphonia devoniensis grows as a tuft of erect, fine, terete branches up to 2.5 cm long and brown in colour.

The cystocarps are ovoid or round or slightly urceolate with a large ostiole.

The tetrasporangia occur spiral series in the branches.