Chrysochromulina cymbium is a unicellular haptophyte alga in the class Prymnesiophyceae. Its species epithet, cymbium (Latin: small boat), likely references cell morphology visible under light microscopy. Like all Chrysochromulina species, it possesses two heterodynamic flagella and a haptonema — the coiling, thread-like appendage unique to haptophytes that functions in prey capture and temporary surface attachment. The cell surface bears organic scales arranged in overlapping tiers, observable under electron microscopy. C. cymbium is a photosynthetic nanoflagellate found in coastal marine environments, where it contributes to primary productivity and carbon cycling. Scandinavian waters have historically yielded the greatest diversity of described Chrysochromulina species, reflecting intensive phycological survey effort in Norway, Sweden, and Denmark. The genus as a whole includes species capable of toxin production during bloom events, posing risks to aquaculture. No formal conservation assessment has been conducted for C. cymbium; it is listed as Not Evaluated by the IUCN. Advances in metabarcoding have revealed that environmental diversity within Chrysochromulina far exceeds the number of formally described morphospecies.