Henri Matisse was a French artist who is often regarded as the most important French painter of the 20th century. He was known for his use of color and his fluid and original draughtsmanship. Along with Pablo Picasso and Marcel Duchamp, he is commonly regarded as one of the three artists who most defined the revolutionary developments in the plastic arts in the opening decades of 20th century. 
From Catherine Bock-Weiss' biography Henri Matisse: Modernist Against the Grain (pp. 147): "Natural enough, since he was surrounded by priests and nuns during his later illnesses and while working on the Venice Chapel, even though he remained a convinced atheist."