What is the earliest age that you have heard of a woman going through menopause?

Premature menopause. Menopause is when the ovaries stop making eggs and your periods no longer come. For most women, this happens in mid to late 40's or early 50s. If your ovaries truly stop working before the age of 40, it is considered abnormally early. There are many conditions that may temporarily stop menstruation, including pregnancy. See your doctor if your periods have stopped and you don't know why.
Early menopause. I have seen 30 year old female with premature ovarian failure. In certain conditions can happen much more earlier.