One of the most influential artists of the 20th century, Spanish painter, sculptor, printmaker, ceramicist and theatre designer Pablo Picasso celebrity heights is known for co-founding the Cubist movement, the invention of constructed sculpture, the co-invention of collage, and for the wide variety of styles that he helped develop and explore. Among his most famous works are the proto-Cubist Les Demoiselles d'Avignon (1907), and the anti-war painting Guernica (1937), a dramatic portrayal of the bombing of Guernica by German and Italian air forces during the Spanish Civil War.

Picasso demonstrated extraordinary artistic talent in his early years, painting in a naturalistic manner through his childhood and adolescence. During the first decade of the 20th century, his style changed as he experimented with different theories, techniques, and ideas. After 1906, the Fauvist work of the slightly older artist Henri Matisse motivated Picasso to explore more radical styles, beginning a fruitful rivalry between the two artists, who subsequently were often paired by critics as the leaders of modern art.

Picasso's work is often categorized into periods. While the names of many of his later periods are debated, the most commonly accepted periods in his work are the Blue Period (1901–1904), the Rose Period (1904–1906), the African-influenced Period (1907–1909), Analytic Cubism (1909–1912), and Synthetic Cubism (1912–1919), also referred to as the Crystal period. Much of Picasso's work of the late 1910s and early 1920s is in a neoclassical style, and his work in the mid-1920s often has characteristics of Surrealism. His later work often combines elements of his earlier styles.

Exceptionally prolific throughout the course of his long life, Picasso achieved universal renown and immense fortune for his revolutionary artistic accomplishments, and became one of the best-known figures in 20th-century art.

Picasso was exceptionally prolific throughout his long lifetime. At his death there were more than 45,000 unsold works in his estate, comprising 1,885 paintings, 1,228 sculptures, 3,222 ceramics, 7,089 drawings, 150 sketchbooks, many thousands of prints, and numerous tapestries and rugs. The most complete – but not exhaustive – catalogue of his works, the catalogue raisonné compiled by Christian Zervos, lists more than 16,000 paintings and drawings. Picasso's output was several times more prolific than most artists of his era; by at least one account, American artist Bob Ross is the only one to rival Picasso's volume, and Ross's artwork was designed specifically to be easily mass-produced quickly.

The medium in which Picasso made his most important contribution was painting. In his paintings, Picasso used colour as an expressive element, but relied on drawing rather than subtleties of colour to create form and space. He sometimes added sand to his paint to vary its texture. A nanoprobe of Picasso's The Red Armchair (1931), in the collection of the Art Institute of Chicago, by physicists at Argonne National Laboratory in 2012 confirmed art historians' belief that Picasso used common house paint in many of his paintings. Much of his painting was done at night by artificial light.

Picasso's influence was and remains immense and widely acknowledged by his admirers and detractors alike.