A cloak is a long, loose outer garment designed to protect the wearer from the elements. Like its relative the cape, a cloak fastens at the throat with one or more clasps, and is cut from a generous swatch of fabric so that it can be draped over multiple layers of clothing. A cloak also often includes a hood as well, to protect the head and neck. Unlike a cape, a cloak is always full length, ideally stretching to the ankles of the wearer, and it also is designed to close fully in front.

The English word “cloak” comes from the Latin clocca, for a traveler's cape. The Latin word is related to the word for “bell,” a reference to the bell like shape of a traditional cloak, which typically flares out from the narrow neck.

Cloaks have been a part of human dress for thousands of years. The simple cut of a cloak means that one can be quickly assembled from any type of textile or hide. Since a cloak provides maximum protection to the individual wearing it, many cultures include cloaks or some variant in their textile history. Cloaks are not widely in fashion in the modern era, and have been largely replaced by fashionable capes, but they are still worn on occasion.

A basic cloak is designed with function in mind. Heavyweight textiles such as wool are usually chosen, for their insulating and water repelling properties. The neck typically closes with a frog or snap, designed to bear the weight of the cloak without opening unexpectedly. If the material is rough, a lining of a softer material is often inserted into the cloak, so that it will not scratch the wearer.

More formal cloaks such as opera cloaks are made from luxury fabrics such as velvet and silk. Although these cloaks may be warming, they are designed primarily with looks in mind. Copious amounts of fabric are often used so that the cloak can be pleated, causing the fabric to drape in folds. A formal cloak may be embroidered or beaded as well. For women who are wearing full dresses, a formal cloak is often a better choice than a coat, since it will not crush the clothing worn underneath.

The garment often plays a role in popular fiction and film, as well. Many re-enactors wear cloaks, since they are associated with numerous periods in history. Fans of fantasy also integrate cloaks into costumes and events, since fantasy fiction and film draw heavily on the medieval period for inspiration. Cloaks are sometimes imbued with magical powers as well, and they are often linked in the imagination with vampires, witches, and other mystical figures.