An adverse consequence of applying morphology-based taxonomic systems to catalog cyanobacteria, which generally are limited in the number of available morphological characters, is a fundamental underestimation of natural biodiversity. In this study, we further dissect the polyphyletic cyanobacterial genus Lyngbya and delineate the new genus Okeania gen. nov. Okeania is a tropical and subtropical, globally distributed marine group abundant in the shallow-water benthos. Members of Okeania are of considerable ecological and biomedical importance because specimens within this group biosynthesize biologically active secondary metabolites and are known to form blooms in coastal benthic environments. Herein, we describe five species of the genus Okeania: O. hirsuta (type species of the genus), O. plumata, O. lorea, O. erythroflocculosa, and O. comitata, under the provisions of the International Code of Nomenclature for Algae, Fungi, and Plants. All five Okeania species were morphologically, phylogenetically, and chemically distinct. This investigation provides a classification system that is able to identify Okeania spp. and predict their production of bioactive secondary metabolites.