Isochrysis Parke 1949

Coccolithophores, cells generally elongate, ellipsoid, dorsiventrally flattened, but metabolic and occasionally subspherical, flagella two inserted subapically, directed anteriorly or posteriorly during swimming, heterodynamic. Haptonema rudimentary, very short, barely detectable with the light microscope, chloroplast one, parietal, with pyrenoid bulging on inner face, small oval body-scales present; very small scales also covering the haptonema, marine, planktonic.

Isochrysis is a genus of haptophytes. It includes the species Isochrysis galbana, Isochrysis litoralis and Isochrysis maritima. Until recently this genus was also thought to contain the 'T-iso' algae frequently used in aquaculture; that species has been reclassified as Tisochrysis lutea.