Cytoplasmic male sterility is total or partial male sterility in hermaphrodite organisms, as the result of specific nuclear and mitochondrial interactions. Male sterility is the failure to produce functional anthers, pollen, or male gametes. Such male sterility in hermaphrodite populations leads to gynodioecious populations (populations with coexisting fully functioning hermaphrodites and male-sterile hermaphrodites).

Cytoplasmic male sterility, as the name indicates, is under extranuclear genetic control (under control of the mitochondrial or plastid genomes). It shows non-Mendelian inheritance, with male sterility inherited maternally. In general, there are two types of cytoplasm: N (normal) and aberrant S (sterile) cytoplasms. These types exhibit reciprocal differences.