Mannan 1,4-mannobiosidase (, 1,4-ò-<small>D</small>-mannan mannobiohydrolase, exo-ò-mannanase, exo-1,4-ò-mannobiohydrolase) is an enzyme with systematic name 4-ò-<small>D</small>-mannan mannobiohydrolase. It catalyses the hydrolysis of (1âÂÂ4)-ò-<small>D</small>-mannosidic linkages in (1âÂÂ4)-ò-<small>D</small>-mannans, to remove successive mannobiose residues from the non-reducing chain ends.