Watanabea is a genus of microscopic green algae in the family Watanabeaceae.

[1] It is widespread in terrestrial and freshwater habitats, including as a photobiont within lichens,[2] but is apparently rare.

[3] Watanabea consists of single, coccoid cells, which are cylindrical to ellipsoid when young, becoming subspherical when mature.

Like Watanabea, members of the family consist mostly of coccoid cells and show a high amount of cryptic diversity.

A key morphological feature in this group is the presence of unequally sized autospores.