A windbreaker, or a windcheater, is a thin fabric jacket designed to resist wind chill and light rain, making it a lighter version of the jacket. It is usually of lightweight construction and characteristically made of a synthetic material. A windbreaker often uses elastic waistbands, and/or armbands, and a zipper to allow adjustments for the current weather conditions.

Regular jackets, coats, etc. may include a type of windbreaker as an interlining that can be removed when desired. Windbreakers sometimes include a hood that may be removable and/or stowable. Many windbreakers may also include large pockets on the inside or the outside which allows belongings to be covered from weather such as light wind or rain as mentioned above. Windbreakers may offer light to moderate insulating protection, more so than a sweater, but less than an overcoat.

Windbreakers are primarily worn during the warmer seasons when wind or rain are expected, or as part of a layering strategy during colder seasons. Brightly colored windbreakers may also be worn by runners as protection from the weather, and as a reflective garment used for safety. A 2012 study demonstrated that adding windbreaker pants and jackets offer a lightweight but effective means of delaying hypothermia if the user is outside walking and encounters unexpected low temperatures.