Authenticity, a key term of modernity, accompanies the differentiation of the modern art system in its various media forms and encompasses important categories such as genuineness, uniqueness, and guarantee as one of its guiding concepts. Authenticity can be related to the author, the work, and the reception. Through numerous examples from the 18th century to the present, the aesthetic concept of authenticity is comprehensively and newly defined in theoretical discourses, poetological programs, and various art forms. Themes such as the history of the concept of authenticity, constructions of subjectivity, forgery and originality, autobiography in literature and art, photography, and documentary film are examined.