Mancozeb is a dithiocarbamate non-systemic agricultural fungicide with multi-site, protective action on contact. It is a combination of two other dithiocarbamates: maneb and zineb. The mixture controls many fungal diseases in a wide range of field crops, fruits, nuts, vegetables, and ornamentals. It is marketed as Penncozeb, Trimanoc, Vondozeb, Dithane, Manzeb, Nemispot, and Manzane.

Mancozeb reacts with, and inactivates, the sulfhydryl groups of amino acids and enzymes within fungal cells, resulting in disruption of lipid metabolism, respiration, and production of adenosine triphosphate. Mancozeb is listed under FRAC code M:03 The "M:" refers to Chemicals with Multi-Site Activity. "M:" FRAC groups are defined as generally considered as a low risk group without any signs of resistance developing to the fungicides.