Vaginal lubrication is the naturally produced lubricating fluid that reduces friction during sexual intercourse. Vaginal dryness is the condition where this lubrication is insufficient.

The lubrication fluid contains water, pyridine, squalene, urea, acetic acid, lactic acid, complex alcohols and glycols, ketones, and aldehydes. The fluid is typically clear or slightly milky in color. It can vary in consistency, texture, color, and odor, depending on sexual arousal, the time of the menstrual cycle, the presence of an infection, or the person's diet.

As a woman becomes sexually aroused, the tissue lining the first inch or so of her vagina, known as the vaginal epithelium (the walls of the vagina), begins to swell and exude a slippery fluid (or modified plasma transudate) out through the hundreds of small ducts buried in the lining. These vaginal juices first appear right inside the vagina, and as the woman’s arousal builds, the secretions will run out the opening. The vulva also has Bartholin glands that produce a lubricating fluid.

The release of this fluid makes vaginal and vulval play more comfortable. It doubtless evolved to ease both penile-vaginal insertion and the movement of sperm up the vaginal canal, increasing the likelihood of impregnation. Under perfect conditions a highly aroused young woman will lubricate profusely. Certain medications, including some over-the-counter antihistamines, as well as life events such pregnancy, lactation, menopause, aging or diseases such as diabetes, will inhibit lubrication. Medicines with anticholinergic or sympathomimetic effects will dry out the "mucosal" or wet tissues of the vagina. Such medicines include many common drugs for allergic, cardiovascular, psychiatric, and other medical conditions.

Safe sex educators warn that vaginal fluids can contain viruses such as HIV, and direct contact with other people's vaginal fluids is therefore discouraged.

When natural lubrification is insufficient, from some illness, lack of sexual desire, nervousness or some other reason, intercourse may be painful. To avoid discomfort, artificial lubrication may be used. Water-based personal lubricants take the form of a gel to apply to the vaginal opening and/or the penis, more rarely of a vaginal suppository to insert prior to intercourse. Other kinds of sexual lubricants exist, but are less commonly used.