Diatoms provide the chief Cenozoic biostratigraphic tool in marine sediments beneath high primary productivity zones, especially where calcareous fossils are rare or poorly preserved. Diatom biostratigraphy, which is based on originations and extinctions of unique taxa, is especially useful in circum-Antarctic, equatorial Pacific, and high latitude North Pacific marine successions, which are available largely from ocean drilling. Oligocene to Holocene diatom biostratigraphic zonations are correlated with the geopaleomagnetic timescale, resulting in age control of million-year to as little as hundred-thousand year resolution. Paleocene and Eocene zonations are less well developed and have lower chronostratigraphic control, but are more widely applicable, because planktonic diatom assemblages of the globally warm early Paleogene were less provincial. We review the principals and methods of biostratigraphy and the application of diatoms to age control in stratigraphic successions worldwide. Distinct biostratigraphic zonations defined for the low latitudes, the North Pacific and the Antarctic, are reviewed, and Atlantic records and Antarctic coastal records are discussed. New biostratigraphic tools are introduced, including multidimensional graphic correlation of published diatom ranges.