Manganese (Mn) is the twelfth most abundant element in the earth’s crust and is widely distributed throughout the surface of the planet, naturally occurring in rocks, soil, water, and food. As an essential trace mineral in diets, Mn is required for a variety of metabolic functions including skeletal system development, energy metabolism, enzyme activation, nervous system function, immune system function, and reproductive hormone function. Manganese has effects on reproductive hormone function as a cofactor for enzymes necessary for cholesterol synthesis. Production of steroid hormones necessary for reproduction is dependent on the availability of cholesterol as a precursor. There is also evidence that Mn has effects on reproduction due to actions at the hypothalamus. Because Mn is used for manufacturing of steel, recent research has focused on the effects of Mn toxicity as a result of occupational endeavors rather than evaluating the optimal Mn inclusion rate for mammalian growth and development, reproductive function, immune function, etc. The objective of this review is to address the functions of Mn in reproduction of animals but there is also a focus on other areas of mammalian biology affected by Mn functions, with an emphasis on domestic swine (Sus scrofa). •Effect of manganese on reproductive function.•Manganese source impacts corpora lutea accumulation.•Excessive manganese may suppress reproduction.