Premature menopause, or Premature ovarian insufficiency, is frequently defined as being menopause that occurs before the age of 40 years, but in the developed world, it is thought that it should be defined as menopause before the age of 45 years, the loss of estrogen having particular long term health risks in this age group.

Premature ovarian insufficiency (POI) is estimated to affect 1% of women under the age of 40 years and 0.1% of women under the age of 30 years.