Guillaume Cornelis van Beverloo, known by his professional pseudonym "Cornielle," was born to Dutch parents in Liege, Belgium. At age twelve his family returned to the Netherlands, where he attended the Academy of Art in Amsterdam from 1940 to 1943. There he studied drawing, but he taught himself how to paint, drawing inspiration from the graphic works of Paul Klee and Joan Miro.

Corneille's first solo show was held in Groningen in 1946, and in 1947 he exhibited alongside his former school cohort Karl Appel at the Gildehuys in Amsterdam. In 1948 he cofounded the CoBrA art movement along with Appel, Christian Dotremont, Joseph Noirot, Constant, and Asger Jorn. The movement, which officially only lasted four years, is still considered one of the most influential movements of post-war Europe. The signature style of CoBrA--simple, immediate, influenced by children's and "primitive" art in an effort to shed the rigidity of pre-war aesthetics--is represented in Corneille's use of bold, playful lines and saturated color. Their first major group exhibition was organized by Willam Sandberg, director of the Stedelijk Museum in 1949. Much like the explosive debut of the Dada movement after World War I, the show was received with outright revolt, and fistfights broke out in the audience as CoBrA read experimental poetry against the backdrop of this new aesthetic.

By the time the group dissolved in 1951, Corneille had settled in Paris, where he would work for the next 60 years. His focus changed to include sculpture and printmaking. He took courses at Stanley William Hayter's Atelier 17, eventually settling on lithography as his printmaking medium of choice. While painting and printing from his studio, he also became active in preserving the CoBrA history through film, exhibitions, and eventually the founding of the CoBrA museum in Amstelveen in 1995. In 1997 he was made a Commander in the Orde cande Nederlandse Leeuw (Order of the Netherlands Lion).

He continued to work until his death in Auvers-sur-Oise, France, in 2010.