Chroococcus minor is a species of cyanobacteria in the family Chroococcaceae, characterized by small spherical cells that occur singly or in pairs within a gelatinous envelope. Like other members of the genus, it is distributed across a range of freshwater and aquatic habitats in temperate regions. Chroococcus species are among the most commonly encountered coccoid cyanobacteria in plankton and periphyton surveys of freshwater ecosystems. They reproduce by binary fission, with daughter cells typically remaining enclosed within the parent sheath for one to two division cycles before dispersing. The blue-green to olive coloration of the cells reflects the presence of phycocyanin, phycoerythrin, and chlorophyll a within specialized membrane structures called thylakoids, which are located in the peripheral cytoplasm. Chroococcus minor has been recorded from Scandinavian and other European freshwater localities. It is representative of the diverse cyanobacterial communities that inhabit the plankton of clear, low-nutrient lakes and the periphyton of streams and lake margins. As a prokaryotic microorganism, its conservation status has not been formally assessed.