Ovarian insufficiency is the inability of the ovary to function effectively in a woman under the age of 40 years. It is considered primary if it fails to respond to appropriate gonadotrophic stimulation and secondary when there is failure on the part of the hypothalamus and pituitary axis to produce appropriate gonadotrophic stimulation. There are various risk factors and associated diseases that can lead to ovarian insufficiency, leading to menstrual irregularities, anovulation, reproductive failure and premature menopause. When POI is suspected, diagnosis is confirmed by measuring serum hormone concentrations of FSH and oestradiol twice ≥1 month apart; levels indicate menopausal range, specifically FSH > 40 units/L and oestradiol < 50 pg/ml. Chromosomal analysis should be performed in all women with non-iatrogenic POI. Management includes counselling with appropriate information and use of appropriate terminology. Treatment is directed towards ovarian hormone replacement, restoration of fertility, and psychological wellbeing. There exists a variety of interventions to prevent iatrogenic ovarian insufficiency resulting from chemo- or radiotherapy.