Psychrobacter is a genus of Gram-negative, osmotolerant, oxidase-positive, psychrophilic or psychrotolerant, aerobic bacteria which belong to the family Moraxellaceae and the class Gammaproteobacteria.

[8] Rudi Rossau found through DNA-rRNA hybridization analysis that Psychrobacter belongs to the Moraxellaceae.

[9] The first species (Psychrobacter immobilis) was described by Juni and Heym.

[10] Psychrobacter occur in wide range of moist, cold saline habitats,[8][11] but they also occur in warm and slightly saline habitats.

[4][12] Hypoacylated lipopolysaccharide (LPS) isolated from Psychrobacter cryohalolentis and Psychrobacter arcticus induces moderate TLR4-mediated inflammatory response in macrophages and such LPS bioactivity may potentially result in the failure of local and systemic bacterial clearance in patients.