Cetyl alcohol is an alcohol commonly used in a variety of cosmetic products. Consumers also can find it listed as "palmityl alcohol" on some labels. It is most commonly used in shampoos and conditioners, as it can make hair feel smooth and soft if used in proper amounts. Cetyl alcohol is a fatty alcohol, meaning that it is derived from fats or oils, and can be used to reduce the surface tension of a liquid. In addition to haircare products, cetyl alcohol is used to thicken lotions and other cosmetics and even to lubricate industrial machine parts, such as bolts and fasteners.

There are many different cosmetic uses for cetyl alcohol; it is commonly present in both skin care and hair care products. Fatty alcohols tend to be rather large molecules and, in sufficient quantities, have an oily texture. This is effective when the goal is to make skin or hair feel soft and smooth, but too much can give hair or skin an unpleasant, unclean oily appearance and feel. Cetyl alcohol is referred to as an emollient because of its ability to soften skin when used in appropriate amounts.

Cetyl alcohol is most commonly used in cosmetic products, but it does have some other applications. It can also be used as a water-based lubricant for non-cosmetic purposes. For example, it is commonly used to lubricate screws, nuts, bolts, pins, and other fastening devices before use. It can be used to lubricate both threaded and non-threaded fastening devices and can greatly improve the ease of use of both, particularly when two fastening devices are not fitting together as well as they should. To effectively lubricate fasteners, one must fully submerge them in the cetyl-alcohol-based lubricant before removing, drying, and using them.

In some cases, cetyl alcohol is used not because of its effect on hair or skin, but because of its overall effect on the chemical structure and stability of a given lotion or substance. For example, it can be used as a thickening agent or as an emulsifier to improve the stability and usability of a cosmetic product. Thickening agents increase the viscosity of a substance, causing it to seem thicker and to hold together better. Emulsifiers can be used to increase the stability of a substance by keeping immiscible, or unmixable, components of the substance dispersed throughout, rather than separated in a manner similar to oil and water.