<div style="float:right;">thumb|upright=0.4</div>
Ulothrix is a genus of green algae in the family Ulotrichaceae. It is a common in fresh to marine habitats, particularly colder and temperate waters. It has a cosmopolitan distribution.
- Ulothrix moniliformis
- Ulothrix implexa
- Ulothrix speciosa
Species of Ulothrix are identified based on the presence/absence of mucilage, the dimensions of cells, characteristics of the cell wall, and characteristics of the akinetes. The taxonomy of the genus is rather poorly known Some of the vegetative cells of Ulothrix can occasionally develop into thick-walled akinetes.