The morphology and genetic affinity of a novel raphidophyte belonging to the genus Chattonella Biecheler is described for the first time from the Oman Sea along the south-east coast of Iran. While morphologically very similar to Chattonella subsalsa Biecheler, the Iranian isolates contain a distinct red eyespot. A comparison of LSU-rDNA and rDNA-ITS show that the Iranian isolate is genetically distinct from other Chattonella subsalsa strains isolated from across a wide global range and indicates that the Iranian isolates representa distinct species related to Chattonella subsalsa.