Early menopause or premature ovarian insufficiency (POI) is a common cause of infertility in women and affects about one per cent of young women. This disorder has significant psychological sequelae and major health implications. Its relevance has increased in recent years due to the fact that age of motherhood is being delayed in developed countries, with the risk of having either primary ovarian insufficiency or less possibilities of pregnancy. The main characteristics are absence of ovulation, amenorrhoea and high levels of serum gonadotropins (hypergonadotropic hypogonadism). Although the aetiology remains uncertain in most cases, several rare specific causes have been elucidated. Potential causes for POI are iatrogenic (ovarian surgery, radiotherapy or chemotherapy), environmental factors, viral infections, metabolic and autoimmune diseases, and genetic alterations. Because of the association with other autoimmune diseases, close follow up is recommended in patients with POI. The traditional indicators to evaluate ovarian ageing are age, serum hormonal levels, anti-Mullerian hormone, antral follicle count, and ultrasonography of ovaries. Hormone replacement therapy remains the mainstay of treatment, and the best chance of achieving a pregnancy is through oocyte donation. This article aims to present an overview of potential causes, clinical manifestations, and treatment options of POI.