Nine macroalgal taxa are reported for the first time from Greece (Aegean Sea and nearby areas): the chlorophyte Cladophora nigrescens , the phaeophyceans Cystoseira susanensis and Dictyopteris lucida, and the rhodophytes Centroceras gasparrinii , Ophidocladus simpliciusculus , Peyssonnelia coriacea , Porphyrostromium ciliare , Radicilingua thysanorhizans and Rodriguezella ligulata . Peyssonnelia stoechas , a species recently reported from Greece (Karpathos Island), is described for the first time from the Gulf of Korinthiakos. Several of the species are rare in the Mediterranean Sea, and five are new to the eastern basin, thus extending their known distribution ranges. Our results indicate that the biodiversity of the eastern Mediterranean marine flora is probably richer than originally thought. A description, illustrations, habitat, geographic distribution and taxonomic remarks are provided for each taxon.