Coccolithophores are calcifying marine phytoplankton of the class Prymnesiophyceae. They are considered to play an import role in the global carbon cycle through the production and export of organic carbon and calcite. We have compiled observations of global coccolithophore abundance from several existing databases as well as individual contributions of published and unpublished datasets. We make conservative estimates of carbon biomass using standardised conversion methods and provide estimates of uncertainty associated with these values. The quality-controlled database contains 57 321 individual observations at various taxonomic levels. This corresponds to 11 503 observations of total coccolithophore abundance and biomass. The data span a time period of 1929-2008, with observations from all ocean basins and all seasons, and at depths ranging from the surface to 500 m. Highest biomass values are reported in the North Atlantic, with a maximum of 127.2 mu gCL(-1). Lower values are reported for the Pacific (maximum of 20.0 mu gCL(-1)) and Indian Ocean (up to 45.2 mu gCL(-1)). Maximum biomass values show peaks around 60 degrees N and between 40 and 20 degrees S, with declines towards both the equator and the poles. Biomass estimates between the equator and 40 degrees N are below 5 mu gCL(-1). Biomass values show a clear seasonal cycle in the Northern Hemisphere, reaching a maximum in the summer months (June-July). In the Southern Hemisphere the seasonal cycle is less evident, possibly due to a greater proportion of low-latitude data. The original and gridded datasets can be downloaded from Pangaea (doi: 10.1594/PANGAEA.785092).