The germline is a key cell lineage fundamental for the generational transmission of genetic information required for the propagation of species. Though few in number, germ cells occupy protected anatomic niches and have numerous unique properties reflecting their privileged role in sexual reproduction and the transmission of DNA. Indeed, the most fundamental distinction among cells in sexually reproducing organisms is that between germ and nongerm (i.e., somatic) cells. Primordial germ cells are formed near the yolk sac and then migrate to colonize the gonadal ridges, where in females germ and somatic cells coalesce to form the ovaries. Ovaries harbor thousands of functional units known as follicles, each comprised of a single oocyte enveloped in a surrounding cohort of specialized somatic cells known as granulosa cells. Meiosis is initiated, but then the primordial follicles become arrested around the time of birth, remaining dormant for years to decades. Their reactivation initiates a lengthy process of follicle maturation culminating in the release of oocytes (ovulation). The complex biology of the female germline and its coalescence with specialized supportive cells to generate follicles—and their subsequent maturation—are the subject of this chapter, with an emphasis on how defects at various steps can lead to infertility or early menopause syndromes.