- a genus of green freshwater protozoans having a reddish eyespot and a single flagellum, found especially in stagnant waters.
- any freshwater unicellular organism of the genus Euglena, moving by means of flagella and typically having holophytic nutrition. It has been variously regarded as an alga or a protozoan but is now usually classified as a protoctist (phylum Euglenophyta)
