A disguise can be anything incognito which conceals one's identity or changes a person's physical appearance, including a wig, glasses, makeup, fake moustache, costume or other items. Camouflage is a type of disguise for people, animals and objects. Hats, glasses, changes in hair style or wigs, plastic surgery, and make-up are also used.

Disguises can be used by criminals, terrorists, secret agents and special forces operators seeking to avoid identification. A person working for an agency trying to get information might go "undercover" to get information without being recognised by the public; a celebrity may go "incognito" in order to avoid unwelcome press attention. Protests often feature people dressed in humorous costumes while political publicity stunts and pranks sometimes employ disguises and imposture. In comic books and films, disguises are often used by superheroes, and in science fiction they may be used by aliens. Dressing up in costumes is a Halloween tradition.

The most basic type of disguise is to use clothing to conceal one's identity. Such a method is commonly used by undercover police investigators, government agents and special forces operators, who go "plainclothes" during a clandestine operation to disguise themselves as an ordinary citizen rather than wearing their typical uniform. Most investigators and agents have a diverse disguise kit that includes makeup and different forms of clothing. Face-obscuring accoutrements can thwart facial recognition systems, making them often used by protesters.

Costumes are usually intended to change one's identity so that they appear to be a certain fictional character and can assume the role of that character. They are an essential tool of actors in entertainment, such as in film and on stage. Costumes can range from simple clothing changes to more elaborate full-body outfits such as mascots.

A realistic disguise can totally change the identity of a person down to their basic appearance, making it impossible to tell who they really are. While realistic latex masks are more commonly seen as a plot device in fiction, they have also been used in real life as well. Creature suits that disguise a person as an animal or monster are used in entertainment, cosplay, as well as hoaxes.

The concept of the human guise is often used by various shapeshifting mythical beings, such as supernatural creatures and deities, to test or fool humans, or allow themselves to pass amongst them without suspicion.

In epic poetry, Odysseus uses the disguise of a beggar to test his family's and servants' loyalty upon his return from a 10-year voyage.

In comic books and superhero fiction, disguises are used to hide secret identities and keep special powers secret from ordinary people. For example, Superman passes himself off as Clark Kent, and Spider-Man disguises himself in a costume so that he cannot be recognized as Peter Parker.