Mammalian ovarian function is under endocrine and neural control. Although the extrinsic innervation of the ovary has been implicated in the control of both ovarian development and mature function, it is now clear that, from rats to humans, the ovary is endowed with a network of intrinsic neurons displaying diverse chemical phenotypes. This article describes the presence of these intrinsic neurons in the ovary of different mammalian species, and discusses the possible functions that they may have in the regulation of ovarian physiology.