Androgen action mediated via the androgen receptor (AR) is long known as vital for male reproductive development and function but the biological role of androgen action in female reproduction is only now being unravelled. Deciphering the specific mechanisms and precise pathways by which AR-mediated actions impact on ovarian function has been hindered by ambiguity of pharmacological investigations relying on aromatizable androgens that also act via estrogen receptors. Using our novel global and cell-specific female AR knockout mouse models we firmly established a role for AR-mediated androgen actions in ovarian function, maintaining optimal female fertility and are deducing the mechanisms of androgen action in governing follicle health, development and ovulation. Furthermore, observational human studies and animal experiments provide substantial evidence for a role of AR-mediated androgen action in the origins of the most frequent ovarian pathology, polycystic ovarian syndrome (PCOS). We have established an optimal PCOS mouse model and, by combining this model with the female AR knockout mouse models, we have provided strong evidence that AR signaling may be an important initiator of PCOS. In concert, these findings illuminate the key roles of AR-mediated androgen action in the optimizing female fertility and ovarian function, as well as providing novel insights into the mechanisms involved in the androgen-associated reproductive disorder PCOS.