Joseph Kosuth (/kəˈsuːt, -ˈsuːθ/; born January 31, 1945) is a Hungarian-American conceptual artist, who lives in New York and Venice, after having resided in various cities in Europe, including London, Ghent and Rome.

Born in Toledo, Ohio, Kosuth had an American mother and a Hungarian father from an old noble family. (A relative, Lajos Kossuth, achieved notability for his role in the Hungarian Revolution of 1848.) Joseph Kosuth attended the Toledo Museum School of Design from 1955 to 1962 and studied privately under the Belgian painter Line Bloom Draper. In 1963 Kosuth enrolled at the Cleveland Institute of Art on a scholarship. He spent the following year in Paris and traveled throughout Europe and North Africa. He moved to New York in 1965 and attended the School of Visual Arts there until 1967. From 1971 he studied anthropology and philosophy with Stanley Diamond and Bob Scholte at the New School for Social Research, New York.

At the School of Visual Arts he made a significant impact while technically a student, influencing fellow students as well as more traditional teachers there at the time such as Mel Bochner. As Kosuth's reputation grew, he was removed from the student body and given a position as a teacher, by Silas Rhodes the founder and President of the school, in 1967. This caused a near revolt of the faculty, as he had been a disruptive presence in the opinion of many of the instructors, several who had unhappily faced his questioning of basic presumptions. His elevation to a teacher was also a result of Kosuth's outside activities, which included the co-founding of the Museum of Normal Art (giving the first exposure to artists such as Robert Ryman, On Kawara, Hanne Darboven, among others) along with proselytizing and organizing artists in a direction which was later identified as the conceptual art movement. Through his art, writing and organizing, he emphasized his interest in the dialectical process of idea formation in relation to language and context. He introduced the notion that art, as he put it, "was not a question of forms and colors but one of the production of meaning." His writing began a re-reading of modernism, initiating a major re-evaluation of the importance of Marcel Duchamp and signaling the shift into what we now identify, in art, as post-modernism. His analysis had a major impact on his practice as an artist and, soon after, on that of others. During this period he also maintained his academic interests. His position on the Faculty, Department of Fine Art, The School of Visual Arts, New York City continued until 1985. He since been Professor at the Hochschule für Bildende Künste, Hamburg, 1988–90; and at the State Academy of Fine Arts Stuttgart, 1991–1997. Currently he is Professor at the Kunstakademie Munich and at the Istituto Universitario di Architettura, Faculty of Design and Art, in Venice. He has been invited as a visiting professor and guest lecturer at various universities and institutions for nearly thirty years, some of which include: Yale University; Cornell University; New York University; Duke University; UCLA; Cal Arts; Cooper Union; Pratt Institute; The Museum of Modern Art, New York; Art Institute of Chicago; Royal Academy, Copenhagen; Ashmoleon Museum, Oxford University; University of Rome; Berlin Kunstakademie; Royal College of Art, London; Glasgow School of Art; The Hayward Gallery, London; The Sorbonne, Paris; The Sigmund Freud Museum, Vienna.

Kosuth continued his work, writing, exhibiting and exhibition organizing and rapidly became acknowledged as one of the pioneers of Conceptual art and installation art; initiating language-based works as well as photo-based works and appropriation strategies since the beginning of his work in the mid-1960s. His activity has consistently explored the production and role of language and meaning within art. Kosuth's nearly thirty-five year inquiry into the relation of language to art has taken the form of installations, museum exhibitions, public commissions and publications throughout Europe, the Americas and the Far East, including five Documenta(s) and four Venice Biennale(s). His earliest work, the Protoinvestigations, were done when he was only twenty years old and as they are considered among the first works of the Conceptual art movement they are included in collections such as The Museum of Modern Art, The Guggenheim, The Whitney, Centre Pompidou, The Tate Gallery, The Reina Sophia, Madrid, among many others, and constitute a youthful record in most of these major collections. Joseph Kosuth's career includes over 170 one-person exhibitions in museums and galleries around the world, twenty-two of them by the time he was twenty-five years old.

In 1989 Kosuth, along with Peter Pakesch, founded The Foundation for the Arts as part of The Sigmund Freud Museum, Vienna. He is the President of the foundation. The foundation was established on the 50th anniversary of Sigmund Freud's death, and is a society of artists engaged, through contributions by members, in forming a collection of contemporary art in honor of and in relevance to Sigmund Freud. The foundation's exhibition space is in the former offices of Anna Freud at the Sigmund Freud Museum, Vienna.

Kosuth belongs to a broadly international generation of conceptual artists that began to emerge in the mid-1960s, stripping art of personal emotion, reducing it to nearly pure information or idea and greatly playing down the art object. Along with Lawrence Weiner, On Kawara, Hanne Darboven and others, Kosuth gives special prominence to language. His art generally strives to explore the nature of art rather than producing what is traditionally called "art". Kosuth's works are frequently self-referential. He remarked in 1969:

Kosuth's works frequently reference Sigmund Freud's psycho-analysis and Ludwig Wittgenstein's philosophy of language.

His first conceptual work Leaning Glass, consisted of an object, a photograph of it and dictionary definitions of the words denoting it. In 1966 Kosuth also embarked upon a series of works entitled Art as Idea as Idea, involving texts, through which he probed the condition of art. The works in this series took the form of photostat reproductions of dictionary definitions of words such as "water", "meaning", and "idea". Accompanying these photographic images are certificates of documentation and ownership (not for display) indicating that the works can be made and remade for exhibition purposes.