Icelandic philologist, critic, and writer in many genres, who played a central role in the cultural life of 20th-century Iceland.

Nordal received his doctorate in Old Norse philology from the University of Copenhagen in 1914, with a thesis on the saga of Saint Olaf (Olaf II Haraldsson). He studied philosophy in Berlin and at the University of Oxford. Upon his return to Iceland in 1918, Nordal was appointed professor of Icelandic language and literature at the University of Iceland. He lectured extensively there and abroad on Icelandic language, literature, and philology. From 1951 to 1957 he was Iceland's ambassador to Denmark, and later he taught at several universities in Europe and the United States.

Nordal published fundamental studies of the Eddic poem Völuspá (1922–23) and many of the Icelandic sagas (Icelanders' sagas). He was instrumental in altering the critical approach to the sagas, showing by careful internal analysis that they are to be regarded more as literary works written by individual writers than as historically accurate products of an oral folk tradition. Notable in this regard is his book Hrafnkatla (1940; Hrafnkel's Saga Freysgoda: A Study). Nordal also wrote many praiseworthy historical works, including a life of the medieval writer Snorri Sturluson (1920) and Íslenzk menning (1942; Icelandic Culture). He published essays, novels, short stories, and poems. His short-story collection Fornar ástir (1919; “Old Loves”) played a significant role in the development of the modern Icelandic short story and the prose-lyric form. Nordal's Íslenzk lestrarbók 1400–1900 (1924; “Icelandic Anthology 1400–1900”) was also influential.