Parabacteroides is a Gram-negative, anaerobic, non-spore-forming genus from the family Tannerellaceae. Currently, the genus Parabacteroides includes eight valid species with standing in nomenclature. The species Parabacteroides faecis and Parabacteroides johnsonii; faeces and Parabacteroides gordonii; blood were all isolated for the first time in humans. Of all the species, Parabacteroides distasonis is the reference type strain for the genus Parabacteroides. To date, Parabacteroides distasonis has been shown to have beneficial effects on colorectal cancer. Multiple researchers have identified that levels of Parabacteroides distasonis in stool are inversely correlated to the presence of intestinal tumors. The evidence for the potential anti-inflammatory effects of Parabacteroides distasonis in colorectal cancer is further supported by the inverse correlation between Parabacteroides distasonis levels and IL-1β production in the gut, suggesting that Parabacteroides distasonis has anti-tumorigenic and anti-inflammatory potential in colorectal cancer patients. Further potential benefits of Parabacteroides distasonis have been identified, particularly in relation to obesity. In addition, several studies have suggested that Parabacteroides distasonis may play a role in various forms of autoimmunity.