钙板金藻（coccolithophores）又名球石藻、颗石藻，属于金黄藻门（Prymnesiophyta）、钙板金藻科、钙板金藻属（Gephyrocapsa），是海洋中的一种单细胞植物，广泛分布于海洋中。

钙板金藻是真核微藻，人类肉眼无法辨识。钙板金藻的细胞壁外会产生二甲基硫（DMS）的化学物质，最后形成盐类逸散到空气中，变成云层的凝结核，使云量增加，抗拒阳光的反射，可以减缓温室效应，对地球有非常重要的贡献。

A coccolithophore (or coccolithophorid, from the adjective ) is a unicellular, eukaryotic phytoplankton (alga). They belong either to the kingdom Protista, according to Robert Whittaker's Five kingdom classification, or Chromalveolata, according to the newer Thomas Cavalier-Smith Biological Classification system. Within the Chromalveolata, the coccolithophorids are in the phylum or division Haptophyta, class Prymnesiophyceae (or Coccolithophyceae). Coccolithophorids are distinguished by special calcium carbonate plates (or scales) of uncertain function called coccoliths, which are also important microfossils. However, there are Prymnesiophyceae species lacking coccoliths (e.g. in genus Prymnesium), so not every member of Prymnesiophyceae is coccolithophorid. Coccolithophores are almost exclusively marine and are found in large numbers throughout the sunlight zone of the ocean.