Fertility is the ability of people or animals to produce healthy offspring in abundance. The term was usually applied to females, but increasingly is applied to males as well, as common understanding of reproductive mechanisms increases and the importance of the male role is better known.

Human fertility depends on factors of nutrition, sexual behavior, culture, instinct, endocrinology, timing, economics, way of life, and emotions. Animal fertility is no less complex, and may display astounding mechanisms.

The opposite is infertility. Some fertility issues here.

By extension fertility is also applied to farmlands and plants, and a large crop of sound fruits, seeds or vegetables is the expectation.

The fertility rate is a demographic measure of the number of children per woman.