In the five-kingdom classification, Chlamydomonas and Chlorella have been included in Kingdom Protista. Kingdom Protista includes unicellular eukaryotes. Kingdom Monera includes prokaryotes.
Earlier, Chlamydomonas and Chlorella were placed in the kingdom Algae. However, according to R. H. Whittaker's classification, the classification depends not only on morphology or physiology but also on phylogeny.