Chroococcus turgidus is a relatively large-celled species of cyanobacteria in the family Chroococcaceae, one of the more frequently cited and widely distributed members of the genus. Its specific epithet turgidus refers to the swollen or turgid appearance of its cells, which are notably rounded and plump. Chroococcus turgidus has been documented from freshwater habitats across a wide geographic range including Europe, North America, Asia, and other regions, reflecting its cosmopolitan distribution. The cells occur in pairs or groups of two to four within a stratified, often amber-brown gelatinous sheath. It is found in the plankton and periphyton of standing and slowly flowing freshwater bodies, on damp soils, and on submerged rocks and other surfaces. Chroococcus turgidus is one of the type or reference species frequently illustrated in classical treatises on freshwater algae and cyanobacteria. Its relatively large cell size compared to other Chroococcus species facilitates identification in microscopic preparations. The species contributes to primary production in freshwater ecosystems and is part of the diverse community of cyanobacteria that inhabit lentic and lotic freshwater environments. It has not been assessed by the IUCN.