The external sex organs are the mons pubis, the vaginal lips (labia), the clitoris and the vaginal opening.

At puberty the mons becomes covered with pubic hair.

Below the mons are the outer vaginal lips (outer labia, labia majora). These are two fleshy folds of skin which extend from the mons downwards between the legs and form the border of the external genital region (vulva). Between the outer vaginal lips lie the inner vaginal lips (inner labia, labia minora). These are thin folds of connective tissue which are well supplied with blood vessels and nerves. They come together at the mons pubis where they form a small hood which covers the clitoris.

The clitoris is a pea-sized body of erectile tissue which is richly supplied with blood vessels and nerves. Touching it leads to sexual arousal. The sexual stimulus causes the erectile tissue to fill with blood and makes the inner vaginal lips swell. At the same time glands located on the inside surface of the inner vaginal lips secrete a fluid into the vaginal vestibule. This makes the vagina become moist and slippery and allows the penis to be introduced more easily. The clitoris is equivalent to the male penis as both are derived from the same embryonic structure.

In a young woman who has not yet had sexual intercourse the vaginal opening is usually covered by a thin membrane called the hymen. A small opening in the hymen a few millimeters in size allows vaginal secretions and menstrual blood to flow out of the vagina. The hymen tears during the first sexual intercourse (defloration) but can also tear before (e.g. during sport, petting, use of tampons).