Polysiphonia denudata (Polysiphonia variegate (C.Agardh) Zanardini) is a small red alga, Rhodophyta, growing as tufts up to 20 cm long without a main branch axis.

[1] Polysiphonia denudata is erect with repeatedly branched axes.

Each branch consists of a central axis with 5 to 7 elongated pericentral cells all of the same length.

Cystocarps are barrel-shaped when mature borne on a wide short stalk.

[1][2] Reported from the north of Ireland in 1847, the specimen is in store in the Ulster Museum, Belfast[3] in England from the south coast,[4] Scottish records considered misidentifications,[5] Netherlands to Portugal and West Africa.