A. niger may refer to: * Acromyrmex niger, an ant species found in southern Brazil and Paraguay * Agelastes niger, the black guineafowl, a bird species found in humid forests of Central Africa * Allocyttus niger, the black oreo, a fish species found around Australia and New Zealand * , a gall wasp species in the genus Andricus * Aspergillus niger, the black mold, a fungus species