KY jelly is a water-based, personal lubricant that is usually used as a lubricant for sexual intercourse or masturbation. Unlike petroleum or oil-based lubricants, it does not react with latex condoms, diaphragms, or sex toys. Sometimes KY Jelly may be used as a substitute for ultrasound gel, to aid insertion of suppositories or tampons, during medical examinations, or for other reasons.

KY Jelly is water-soluble and its main lubricating ingredients are glycerol (glycerine) and hydroxyethylcellulose. Antiseptic and preservative additives include chlorhexidine gluconate, gluconolactone, methylparaben, and sodium hydroxide. Ingredients may vary slightly between the different KY products. KY Jelly does not contain any added colors or perfumes.

KY Jelly is non-greasy but may dry out during use. The lubricating effects can be reactivated with the addition of water or saliva. Because glycerol is one of its ingredients, KY Jelly has a slightly sweet taste. It does not stain fabric.