The most influential Norwegian writers of the late 19th century were Jonas Lie, Alexander Kielland, Bjørnstjerne Bjørnson (also the author of the Norwegian national anthem), and of course Henrik Ibsen. They're known as The Four Greats even today, although the honorific was not given to them by readers, critics, or even (necessarily) history...but by their publisher, who needed a marketing hook for advertising purposes.
A unity of purpose pervades the whole period, creation of a national culture based on the almost forgotten and certainly neglected past, as well as celebration of the Bonde Kultur or Norwegian farm culture. The realism of Kielland (e.g., Skipper Worse) gave way to the romantic and nationalistic spirit which swept Europe rekindled and the Norwegian interest in their glorious Viking past (e.g., Ibsen’s The Vikings at Helgeland), the struggles of the Middle Ages (e.g., Ibsen’s Lady Inger of Østeraad), peasant stories (e.g., Bjørnson’s A Happy Boy) and the wonders of myths and folks tales of the mountains (e.g., Ibsen’s Peer Gynt) and the sea (e.g., Lie’s The Visionary).Courtesy Wikipedia
Knut Hamsun, a controversial figure in Norway later in his life, was the most prominent author of modernist literature.
The young Hamsun objected to realism and naturalism. He argued that the main object of modern literature should be the intricacies of the human mind, that writers should describe the "whisper of blood, and the pleading of bone marrow".Hamsun is considered the "leader of the Neo-Romantic revolt at the turn of the century", with works such as Hunger (1890), Mysteries (1892), Pan (1894), and Victoria (1898). His later works—in particular his "Nordland novels"—were influenced by the Norwegian new realism, portraying everyday life in rural Norway and often employing local dialect, irony, and humour. The epic work Growth of the Soil (1917) earned him the Nobel Prize.
Hamsun is considered to be "one of the most influential and innovative literary stylists of the past hundred years" (ca. 1890–1990). He pioneered psychological literature with techniques of stream of consciousness and interior monologue, and influenced authors such as Thomas Mann, Franz Kafka, Maxim Gorky, Stefan Zweig, Henry Miller, Hermann Hesse, and Ernest Hemingway.Courtesy Wikipedia
Hamsun's legacy is not without controversy; he was charged with treason due to his outspoken Nazi sympathies during WWII. He was confined to a psychiatric hospital after the war, and after examination, it was concluded that he had "permanently impaired mental faculties", and the charges were dropped.
In the early 20th century, three novelists from Norway won the Nobel prize in literature: Bjørnstjerne Bjørnson; Knut Hamsun (for Markens Grøde, Growth of the Soil, 1917) in 1920; and Sigrid Undset for the Kristin Lavransdatter trilogy in 1927.