Born in Dessau, Germany, in 1940 Knoebel studied at the Darmstadt Werkkunstschule under László Moholy-Nagy. He later studied under Joseph Beuys at the Kunstakademie Düsseldorf with fellow students Blinky Palermo (with whom he shared a studio), and Jörg Immendorff.
Knoebel's work explores the relationship between space, picture support and colour. The style and formal concerns of his painting and sculpture have drawn comparisons with the high modernist principles of both Kazimir Malevich and the Bauhaus.
Between 1966 and 1969, Knoebel worked on a series of Linienbildern, or line paintings, totalling some 90 panels. Another series of 250,000 Linienbilder drawings were done on A4 sheets between 1969 and 1973/75.
Beginning in 1968, Knoebel was one of the first Beuys students to use photography as an independent artistic medium. From the mid-1970s on, Knoebel then turned towards a gestural use of color on layered plywood boards or metal plates. Knoebel made a series of 24 colourful monochromes in homage to his friend Blinky Palermo after Palermo’s death in 1977. The monumental series was acquired by Dia Art Foundation.
In June 2011, Knoebel made six stained-glass panes for Notre-Dame de Reims Cathedral which stand alongside the windows of Marc Chagall.
Knoebel's works are held worldwide in numerous public collections including Dia:Beacon in Beacon, New York; The Museum of Modern Art in New York City; the Albertina in Vienna; Berardo Collection Museum Lisbon in Portugal; National Museum of Contemporary Art Korea; Kunstsammlung Nordrhein-Westfalen in Germany; Gemeentemuseum Den Haag in Netherland and Malmö Konsthall in Sweden.