The traditional green algal genus Chlorella, which comprised coccoid algae surrounded by a smooth cell wall and reproducing solely by autosporulation, has proved to be polyphyletic and extremely diverse in phylogenetic terms. We studied a new subaerial Chlorella-like strain CAUP H7901 and morphological, ultrastructural, and molecular phylogenetic investigations indicated that it represents a new lineage of the trebouxiophycean Watanabea clade, dissimilar from other members of this group. The alga has globular coccoid cells with a single parietal pyrenoid-bearing chloroplast. The pyrenoid is transected by multiple radial thylakoid bands. The alga reproduces exclusively by means of asexual autospores of unequal size. In 18S rDNA sequence phylogenies, it was nested within the Watanabea clade close to lineages containing Chlorella saccharophila, Chlorella luteoviridis, Heveochlorella hainangensis, and two uncharacterized strains, but alternative positions within the Watanabea clade could not be rejected by an approximately unbiased (AU) test. Here we describe this organism as a new genus and species Kalinella bambusicola gen. et sp. nov. Furthermore, we describe Heterochlorella gen. nov. to accommodate a species previously referred to as Chlorella luteoviridis.