Coccolithus pelagicus is one of the most ecologically important and geologically significant coccolithophores—single-celled marine phytoplankton in the class Prymnesiophyceae—and has an extraordinary fossil record extending back over 60 million years. This species produces two distinct morphological forms: a motile haploid phase bearing organic body scales (Crystallolithus hyalinus stage) and a non-motile diploid phase bearing large, robust calcite coccoliths (Coccolithus pelagicus sensu stricto). The coccoliths of C. pelagicus are among the largest and heaviest produced by any extant coccolithophore, and their high carbonate content makes them disproportionately important in ocean carbonate export to the seafloor. The species inhabits cool-temperate to subpolar waters of the North Atlantic and North Pacific, with high abundances reported in Norwegian and North Atlantic waters, making it a dominant component of high-latitude coccolithophore communities. As a major contributor to the biological carbon pump, C. pelagicus is a critical link between atmospheric CO₂ drawdown and deep-ocean carbon sequestration. During bloom events, cell densities can reach hundreds of cells per milliliter. The species also contributes dimethylsulfoniopropionate (DMSP) to the water column, a precursor to dimethyl sulfide (DMS), which influences marine cloud formation and regional climate. Its extensive geological record makes it invaluable as a biostratigraphic marker in deep-sea sediment cores. Conservation status is not formally evaluated.