The common and ecologically important cyanobacterial form-genus Leptolyngbya is widely distributed in numerous ecosystems over the Earth's biosphere. Several morphospecies dominate microbial communities in polar habitats, but their diversity and local ecological significance are little known. Several articles characterising strains isolated from Antarctic coastal habitats by molecular methods were published, but knowledge of their phenotype and ecological characters are indispensable for future detailed environmental studies. Distinct morpho- and ecotypes (ecologically important morphospecies) from maritime Antarctica are characterised in this article. Eight dominant Leptolyngbya types from subaerophytic and freshwater habitats were recognised, and four of them (L. borchgrevinkii, L. fritschiana, L. nigrescens and L. vincentii) are described as new distinct species.