Five cyanobacterial strains with Nostoc-like morphology from different localities of the Mazandaran province of Iran were characterized using a polyphasic approach. Three strains clustered within the Aliinostoc clade whereas one each of the remaining two strains clustered within the genera Desmonostoc and Desikacharya. The phylogenetic positioning of all the strains by the bayesian inference, neighbour joining and maximum parsimony methods inferred using 16S rRNA gene indicated them to represent novel species of the genera Aliinostoc, Desmonostoc and Desikacharya. The 16S-23S ITS secondary structure analysis revealed that all five strains under study represented novel species unknown to science. In accordance with the International Code of Nomenclature for algae, fungi and plants we describe three novel species of the genus Aliinostoc and one species each of the genera Desmonostoc and Desikacharya.