Azomonas agilis is a species of motile, Gram-negative bacteria found in water and is capable of fixing atmospheric nitrogen. It is the type strain for the genus Azomonas. A. agilis resembles protists with its ovoid, ellipsoidal, or coccoid cells. The cells are relatively large, usually 2.5-6.4 μm long and 2.0-2.8 μm wide, though giant cells that are 10.0-13.5 μm have been described. The cells have peritrichous flagella which enable motility. The species also produces a diffusible yellow-green or red-violet pigment which fluoresces bluish-white under ultraviolet light.