Nicolaas Thomas Bernhard (German: [ˈtoːmas ˈbɛʁnhaʁt]; 9 February 1931 – 12 February 1989) was an Austrian novelist, playwright, poet and polemicist who is considered one of the most important German-language authors of the postwar era. He explored themes of death, isolation, obsession and illness in controversial literature that was pessimistic about the human condition and highly critical of post-war Austrian and European culture. He developed a distinctive prose style often featuring multiple perspectives on characters and events, idiosyncratic vocabulary and punctuation, and long monologues by protagonists on the verge of insanity.

Born in the Netherlands to his unwed Austrian mother, for much of his childhood he lived with his maternal grandparents in Austria and in boarding homes in Austria and Nazi Germany. He was closest to his grandfather, the novelist Johannes Freumbichler, who introduced him to literature and philosophy. As a youth, he contracted pleurisy and tuberculosis and lived with debilitating lung disease for the rest of his life. While recovering in a sanatorium he began writing poetry and stories and met Hedwig Stavianicek, a wealthy heiress who supported his literary ambitions and whom he later described as the most important person in his life.

After his breakthrough novel Frost (1963), he established himself over the next 20 years as a leading novelist and playwright in German. His major works include the novels Correction (1975) and Extinction (1986) and his memoirs Gathering Evidence (1975–82). George Steiner called him "at his best, the foremost craftsman of German prose after Kafka and Musil". He influenced the Austrian vernacular and a younger generation of Austrian writers including Elfriede Jelinek.

Bernhard was controversial in Austria for his public polemics against what he saw as his homeland's post-war cultural pretensions, antisemitism, provincialism, and denial of its Nazi past. While critics labelled him a Nestbeschmutzer (one who fouls his own nest), he described himself as a troublemaker. He died of heart failure in his apartment in Gmunden, Upper Austria, in February 1989. Controversy extended beyond his death when it was revealed that his will sought to prohibit the publication or performance of his works in Austria for 70 years.

Thomas Bernhard was born on 9 February 1931 in Heerlen, the Netherlands, where his unmarried Austrian mother, Herta Bernhard, worked as a maid. In the autumn of 1931, Herta took Thomas to Vienna to live with her parents: Anna Bernhard and her de facto husband, the novelist Johannes Freumbichler. (Thomas never met his biological father, Alois Zuckerstätter, who refused to acknowledge him and committed suicide in 1940.)

In 1935, Herta's parents moved with Thomas to Seekirchen, near Salzburg. In 1936, Herta married Emil Fabjan and the following year moved with him and Thomas to Traunstein, Bavaria, in Nazi Germany. Fabjan never adopted Thomas, and Bernhard always referred to him as his guardian rather than his stepfather. Herta's parents moved to the nearby village of Ettendorf in 1939. Bernhard was closest to his grandfather and later called him "an anarchist, if only in spirit." Freumbichler introduced Bernhard to literature and philosophy and was a major influence on his life.

Bernhard was miserable in the Nazi school system where he was required to join the Deutsches Jungvolk, a branch of the Hitler Youth, which he hated. At age eight, he was sent to a home for maladjusted children and at age 12 to a boarding school in Salzburg where he experienced allied bombing raids. After the war, the Fabjan and Freumbichler families moved to Salzburg where Bernhard continued his schooling. In 1947, Bernhard left school to start an apprenticeship with a grocer.

Bernhard took private singing lessons and aspired to become an opera singer. In early 1949, he developed pleurisy and was eventually diagnosed with tuberculosis. He stayed in various hospitals and sanatoriums until January 1951. Bernhard's grandfather died in 1949 and his mother died of cancer the following year.