Enrico Castellani, born in the province of Rovigo, he studied art and architecture at the Brera Academy in Milan and later in Brussels. He settled in Milan at the end of the 1950s and met Piero Manzoni. After an initial phase with informal painting, which looked to the interpretation of signs expressed by the American Mark Tobey, he and Manzoni founded the magazine Azimuth, of which only two issues were published between 1959 and 1960. The magazine saw the publication of texts by Vincenzo Agnetti, Gillo Dorfles, Guido Ballo, Manzoni himself, and poems by Nanni Balestrini, Edoardo Sanguineti, Elio Pagliarani, Leo Paolazzi and others. Together with Manzoni, Castellani founded the Azimut gallery, with a life almost as short as that of the magazine that had a nearly identical name.
The first relief surfaces created by Castellani date back to 1959, and mark the beginning of meticulous and coherent research in which the surface of the canvas is turned outwards through the use of nails on the back; set in linear sequences, they create a rhythmic movement on the front side of the canvas. Such research was in line with the expressive zeroing advocated by the Zero group (which worked with Azimut/h and which Piero Manzoni was part of) and can be found in European and American minimalist optical kinetic research: it is said that Donald Judd, one of the leaders of American Minimal Art, called Castellani the father of minimalism.
He was one of the leading figures in a number of key exhibitions from the 1960s onwards: in 1967 he took part in the exhibition in Foligno Lo spazio dell'immagine with Ambiente bianco, taking part in several Venice biennials, starting in 1964. The following year he exhibited at the exhibition The Responsive Eye at MoMA, in 1970 he took part in the exhibition Vitalità del negativo nell'arte italiana, in Rome and in 1981 he was invited by Germano Celant to participate in Identité Italienne. L'art en Italie depuis 1959 at the Centre Pompidou in Paris.
In 2001 Fondazione Prada dedicated an extensive retrospective to Castellani's work in Milan. His works are on display in galleries, museums and institutions around the world, including the Italian Embassy in Tokyo, and in 2010 he received the Praemium Imperiale from the Japan Art Association.