Chroomonas mesostigmatica is a species of cryptophyte alga in the family Chroomonadaceae, described from freshwater environments. The specific epithet mesostigmatica likely refers to a centrally positioned stigma — a photoreceptive structure — within the cell, distinguishing this species morphologically from others in which the stigma is positioned differently. The stigma or eyespot in flagellate algae is associated with photoreception, enabling the cell to orient its swimming direction toward or away from light sources in a process called phototaxis. This capability is ecologically important for optimizing position in the water column relative to light availability and nutrient distribution. Chroomonas species are biflagellate, swimming with characteristic rapid, slightly helical motility. The cells contain cryptophyte-type plastids with phycobiliproteins and chlorophyll a and c. Chroomonas mesostigmatica has been documented from European freshwater habitats, contributing to the diverse microalgal communities of lakes, ponds, and slow-flowing waters. Its ecological roles include primary production and participation in the microbial loop through grazing by heterotrophic flagellates. The species has not been assessed by the IUCN.