Polysiphonia stricta is a small red marine alga in the Division Rhodophyta.

Polysiphonia stricta forms dense clumps of branching axes.

[2][3] Spermatangial branchlets are formed in clusters at the apices.

The tetraspores are in series in the final branches.

[2] Epizoic and epiphytic in the low littoral to 20 m.[2] Found around the British Isles, the West Atlantic and American Atlantic.