Male sterility in plants can be caused by nuclear genes alone as well as linked mitochondrial genes or both; these circumstances are referred to as cytoplasmic male sterility (CMS) and genetic male sterility (GMS), respectively. Cytoplasmic male sterility and genetic male sterility allow it to be easier to produce hybrid seeds in various crops, enabling breeders to take advantage of the yield increases hybrid vigour in form of heterosis. The specificity, incidence, and restoration of fertility of CMS in are regulated by multiple levels of interaction between mitochondrial and nuclear genes. Environment-sensitive GMS (EGMS) mutants may be subject to epigenetic regulation by noncoding RNAs and have the ability to recover their fertility under various growth conditions, making them valuable breeding stock for the development of hybrid seeds. The general types of male sterility, such as the GMS, CMS, CGMS, and EGMS systems, are discussed in the current chapter along with their evolutionary significance for crop reproductive systems.