Tetradesmus is a genus of green algae in the family Scenedesmaceae.

[2] Species of Tetradesmus are found in a variety of habitats, including fresh water and biological soil crusts in deserts.

It was not universally accepted; Robert Hippolyte Chodat synonymized the genus into Scenedesmus, while George Stephen West accepted the genus as separate from Scenedesmus.

[4] In the 2000s, molecular data revealed found that Scenedesmus was polyphyletic.

[4] As Tetradesmus species are phylogenetically closely related to species once placed in Scenedesmus subgenus Acutodesmus, the genus Acutodesmus was raised to genus rank and Tetradesmus was placed as a synonym of Acutodesmus.