Joseph Cornell (December 24, 1903 – December 29, 1972) was an American visual artist and filmmaker, one of the pioneers and most celebrated exponents of assemblage. Influenced by the Surrealists, he was also an avant-garde experimental filmmaker. He was largely self-taught in his artistic efforts, and improvised his own original style incorporating cast-off and discarded artifacts. He lived most of his life in relative physical isolation, caring for his mother and his disabled brother at home, but remained aware of and in contact with other contemporary artists.

Joseph Cornell was born in Nyack, New York, to Joseph Cornell, a textiles industry executive, and Helen Ten Broeck Storms Cornell, who had trained as a nursery teacher. Both parents came from socially prominent families of Dutch ancestry, long-established in New York State. Cornell's father died April 30, 1917, leaving the family in straitened circumstances. Following the elder Cornell's death, his widow and children moved to the borough of Queens in New York City. Cornell attended Phillips Academy in Andover, Massachusetts, in the class of 1921. Although he reached the senior year, he did not graduate. Following this, he returned to live with his family.

Except for the three-and-a-half years he spent at Phillips, he lived for most of his life in a small, wood-frame house on Utopia Parkway in a working-class area of Flushing, along with his mother and his brother Robert, whom cerebral palsy had rendered physically disabled. Aside from his time at Andover, Cornell never traveled beyond the New York City area.

Cornell's most characteristic art works were boxed assemblages created from found objects. These are simple shadow boxes, usually fronted with a glass pane, in which he arranged eclectic fragments of photographs or Victorian bric-a-brac, in a way that combines the formal austerity of Constructivism with the lively fantasy of Surrealism. Many of his boxes, such as the famous Medici Slot Machine boxes, are interactive and are meant to be handled.

Like Kurt Schwitters, Cornell could create poetry from the commonplace. Unlike Schwitters, however, he was fascinated not by refuse, garbage, and the discarded, but by fragments of once beautiful and precious objects he found on his frequent trips to the bookshops and thrift stores of New York. His boxes relied on the Surrealist use of irrational juxtaposition, and on the evocation of nostalgia, for their appeal.

Cornell often made series of boxed assemblages that reflected his various interests: the Soap Bubble Sets, the Medici Slot Machine series, the Pink Palace series, the Hotel series, the Observatory series, and the Space Object Boxes, among others. Also captivated with birds, Cornell created an Aviary series of boxes, in which colorful images of various birds were mounted on wood, cut out, and set against harsh white backgrounds.

In addition to creating boxes and flat collages and making short art films, Cornell also kept a filing system of over 160 visual-documentary "dossiers" on themes that interested him;^{[citation needed]} the dossiers served as repositories from which Cornell drew material and inspiration for boxes like his "penny arcade" portrait of Lauren Bacall. He had no formal training in art, although he was extremely well-read and was conversant with the New York art scene from the 1940s through to the 1960s.^{[citation needed]}

His methodology is described in a monograph by Charles Simic as: