Selenastrum is a genus of green algae in the family Selenastraceae.

[1] The genus was circumscribed by the German phycologist Paul Friedrich Reinsch in 1866.

[3] Like other members of the family, Selenastrum reproduces asexually, by forming autospores.

The two genera have sometimes been considered congeneric,[7] but molecular phylogenetic studies have shown them to be found in different clades.

[8] In 2016, the genera Messastrum and Curvastrum were created, differing from Selenastrum mainly in their 18S rDNA and rbcL gene sequences.