A costume store is a retail space specializing in the sale and/or rental of clothing worn for fun in order to adopt another identity or to play a role outside of one's normal routine. The costumes, masks, disguises, and exotic or outlandish clothing offered in a costume store may represent recognizable persons, animals, or archetypes, or it may be different from the mainstream without creating any recognizable image.

Costume stores typically do a high percentage of their business around Halloween. They also cater to theaters, costume parties, and private role-playing.

The clothing supports disguise, performance, or an adopted identity outside everyday dress. It need not depict a recognizable character, and a traditional clothing store is instead identified by its regional, national, or cultural clothing specialization.