Pio Baroja y Nessi (1872-1956), Spanish novelist, whom many critics regard as the leading Spanish novelist of the 20th century. He was born in San Sebastián and educated in Madrid as a physician. His first novel was The House of Aizgorri (1900; translated 1958). It forms part of the trilogy La tierra vasca (The Basque Country, 1900-09), which also includes The Lord of Labraz (1903; translated 1926), one of his most admired novels. The work for which he is best known outside Spain is the trilogy The Struggle for Life (1904; translated 1922-24), a moving description of life in the slums of Madrid. His Memorias de un hombre de acción (Memories of a Man of Action; 20 volumes, 1913-31), consists of a series of loosely connected episodes revolving around one of his ancestors who lived in the Basque Country at the time of the Carlist uprisings early in the 19th century. Baroja's published writings total more than 100 volumes.

Using the Spanish picaresque tradition, Baroja chose for his protagonists the misfits and outcasts of society, and his novels, although crammed with lively incident, usually lack plots. A master of the realistic portrayal of character and setting, especially when he draws on his knowledge of the Basque country and people, his style is abrupt, vivid, and impersonal, and his philosophy is pessimistic.