Premature ovarian failure (POF) affects 1% of women in reproductive age, but its etiology remains uncertain. While kisspeptins, the products of Kiss1 that act via Kiss1r (aka, Gpr54), are known to operate at the hypothalamus to control GnRH/gonadotropin secretion, additional actions at other reproductive organs, including the ovary, have been proposed. Yet, their physiological relevance is still unclear. We present here a series of studies in Kiss1r haplo-insufficient and null mice suggesting a direct role of kisspeptin signaling in the ovary, whose defect precipitates a state of primary POF. Kiss1r hypomorph mice displayed a premature decline in ovulatory rate, followed by progressive loss of antral follicles, oocyte loss and a reduction in all categories of pre-antral follicles. These alterations were accompanied by reduced fertility. Because of this precocious ovarian ageing, >48-wk mice showed atrophic ovaries, lacking growing follicles and corpora lutea. This phenomenon was associated to a drop in ovarian Kiss1r mRNA expression, but took place in the absence of a decrease in circulating gonadotropins. In fact, FSH levels increased in aged hypomorph animals, reflecting loss of follicular function. In turn, Kiss1r null mice, which do not spontaneously ovulate and have arrested follicular development, failed to show normal ovulatory responses to standard gonadotropin priming, and required GnRH pre-stimulation during 1-wk in order to display gonadotropin-induced ovulation. Yet, the magnitude of such ovulatory responses was ∼half of that seen in control immature WT animals. Altogether, our data are the first to demonstrate that Kiss1r haplo-insufficiency induces a state of POF, which is not attributable to defective gonadotropin secretion. We also show that the failure of follicular development and ovulation linked to the absence of Kiss1r cannot be fully rescued by (even extended) gonadotropin replacement. These findings suggest a direct ovarian role of kisspeptin signaling, whose perturbation may contribute to the pathogenesis of POF.