The chaos entity was an intelligent species which lived in chaotic space. They existed on a perceptual wavelength which was undetectable to most humanoid senses.
In 2375, Chakotay, who had the gene for a cognitive disorder, detected the chaos entities presence as the USS Voyager traveled through the space they lived in. After communication was established, with Chakotay acting as a liaison, the entities helped the crew of the Voyager in escaping chaotic space. (VOY: "The Fight")
This species was not named in the episode. The name was from the Star Trek Encyclopedia, 4th ed., vol. 1, p. 133.