Christiaan Karel Appel (pronounced [ˈkrɪstijaːŋ ˈkaːrəl ˈɑpəl] ⓘ; 25 April 1921 – 3 May 2006) was a Dutch painter, sculptor, and poet.

His parents opposed his choice to become an artist, leading him to leave home; this was also necessary because he needed to hide from the German police so that he would not be picked up and sent to Germany to work in the weapons industry.

In 1949 he participated with the other CoBrA artists in the Stedelijk Museum Amsterdam; this generated a huge scandal and many objections in the press and public.

In 1947 he started sculpting with all kinds of used materials (in the technique of assemblage) and painted them in bright colors: white, red, yellow, blue, and black.

He joined the Experimentele Groep in Holland [nl] together with the young Dutch painters Anton Rooskens, Theo Wolvecamp, and Jan Nieuwenhuys.

In 1948 Appel joined CoBrA (coined by the Belgian poet Christian Dotremont from the initials of the members' home countries' capital cities: Copenhagen, Brussels, Amsterdam) together with the Dutch artists Corneille, Constant, and Jan Nieuwenhuys.

[2] Appel used this very intensively; his 1949 fresco 'Questioning Children' in Amsterdam City Hall caused controversy and was covered up for ten years.

As a result of this controversy and other negative Dutch reactions to CoBrA, Appel moved to Paris in 1950 and developed his international reputation by travelling to Mexico, the United States, Yugoslavia, and Brazil.

[11] In the wake of his death, the Foundation (based in Amsterdam) functions as his official estate in addition to its primary service as an image archive.