The former nomenclature for the Gram-negative coccobacillus of the family Enterobacteriaceae now known as Yersinia pestis - etiologic agent of bubonic plague. So named because of the affiliation of its discoverer, Alexandre Yersin, with the Pasteur Institute.

The name Pasteurella pestis was in use until quite recently, and older works on the subject of the Black Death often refer to the bacillus by this name, which can cause some confusion.