Euglena viridis is a freshwater single-celled microalgae that acts as a mixotroph and possesses a secondary chloroplast. Unlike some other Euglena species, its chloroplast is encased in three membranes and lacks a nucleomorph. Typically, Euglena viridis measures between 40 and 65 μm in length, making it slightly larger than the more commonly known Euglena gracilis.