Painter, aculptor, deisgner, and printmaker Christiaan Karel Appel was born in Amsterdam, Holland on April 25th, 1921. As a teenager, Appel apprenticed at his father's barber shop and it wasn't until his uncle, Karel Chevalier, gave him a box of oil paints that he began to pursue art at age 15. He first studied with his uncle but before long the elder Karel realized his nephew had surpassed him. He he took Appel to his own painting instructor, Jozef Verheijen, to train. Around this time Appel also created his first sculpture, though it would be some time before he returned to the medium.

As it was between World Wars in a neutral country, Karel Appel was exposed from a distance to the sea change of the international art world. Though much of Europe attempted to return to the quietude of classical genres during the recovery ("La retour a l'ordre"), there were also pockets of Avant-garde and other fringe genres that went against the grain in protest, and soon bore more significance as the world's political spectrum became unstable once again. In 1939 Appel left his family home and moved into his own studio, rooming with the anarchist Henk Eikeboom.

As it became increasingly clear that Germany was aiming to occupy the Netherlands, Appel attempted to enter into the Royal Academy of Fine Arts, Amsterdam in 1941, knowing a student status would allow him to stay out of the way of the Nazis despite his anarchistic leanings. His first attempt failed, and he began traveling throughout the countryside, sketching and keeping to himself. In 1942 he was finally accepted into the academy, where he studied Modernism and Surrealism as well as the poetry of Walt Whitman. His work from this time was greatly influenced by Picasso, Matisse, and Dubuffet, and he became close friends with the artist Corneille. In 1944, having completed of his studies, Appel no longer had the protected status of a student; his artwork and lifestyle make him a target of Nazi suspicion. He was accused of aiding Allied sympathizers, and he went into hiding.

In 1945 he returned to Amsterdam and remained transient, staying and traveling with Corneille. He held his first solo exhibition at the Het Beerenhuis in Groningen and was a part of the Jonge Schilders (Young Painters) exhibit at the Stedelijk Museum in Amsterdam, alongside Corneille, Eugene Brands, and Anton Rooskens. Two years later he visited Paris for the first time, where he was exposed to the work of Edouard Pignon, Jean Dubuffet, and Constant, whose works changed the course of Appel's style. After returning home, he began working on three dimensional works including reliefs and sculptures made of found objects. By 1948 he has begun to create a reputation for himself in the Netherlands and the collector Martin Visser invited Appel, Corneille, and Constant to show their works at the De Bijenkorf department store. Before long Appel began exhibiting regularly, and his painting "Sailor's Girl" was purchased by the Stedelijk Museum Amsterdam. Along with Corneille and Constant, Appel founded the experimental group and magazine Reflex, which soon thereafter merged with the CoBrA movement. It was in Paris, where he had an exhibition in 1949 and took up residence in 1950, that Appel truly mastered his creative powers. He worked freely with color, which he applied in thick blotches as a reaction against the geometric Academicism inherited from neoplasticism, and his subject matter was both broad-ranging and powerful.

CoBrA dissolved in 1951 afer disagreements between the artists, and Appel began to associate with Abstract Expressionists including Jackson Pollack, Georges Mathieu, Sam Francis, and others. In 1953 James John Sweeney, then director of the Guggenheim museum, visited Appel's studio and purchased two of his paintings and selected his work for the Young European Painters exhibition later that year. In 1954 he won the UNESCO award at the 27th Venice Biennale, representing the Netherlands, and was given a solo exhibition in New York at the Martha Jackson gallery.

His frist trip to the United States took place in 1957 where he lived on Long Island for the summer. His exposure to American Abstract artists as well as jazz musicians and other luminaries once again changed the course of his work, and he began working on polychrome sculptures, stained-glass windows, and mural paintings using explosive color and line. This led to a commission by UNESCO to paint a mural on the wall of its Paris headquarters' restaurant. (Rencontre du printemps now hangs in its conference room.)

Appel remained prolifically active for the next four decades, exhibiting internationally. His oeuvre included theater and opera set deisgns and experimental films, and he received numerous commissions and awards. Among them was the Knight of the Second Degree, Commander of the Order of the Netherlands Lion award from the Dutch government and the French Legion d'Honneur, Officier status. In 1990 a retrospective of his work, entitled Ik wou dat ik een vogel (If I Were a Bird), opened at the Gemeentemuseum Den Haag and traveled to Germany, Spain, and Austria. That same year plans for the Karel Appel Foundation began, and in 2000 it was officially established in Amsterdam.

He remained active until very near his death in Zurich on May 3, 2006. His last major exhibition took place in 2005, and included new paintings of nudes highlighted by neon tubes, shown at the Gemeentemuseum.

An extensive chronology of Appel's life and work, along with a complementary timeline of world events and their effect on his career, can be found on his foundation's website.