Icelandic playwright who became internationally famous for one play, Fjalla-Eyvindur (1911; Danish Bjærg-Ejvind og hans hustru, 1911; Eyvind of the Mountains; filmed 1917, by Victor Sjöström), which created a sensation in Scandinavia and in Germany and was later produced in England and the United States. Some contemporary critics hailed him as a peer of Henrik Ibsen (Ibsen, Henrik), B.M. Bjørnson (Bjørnson, Bjørnstjerne Martinius), and August Strindberg (Strindberg, August)—but his other plays were less successful.

The son of a wealthy farmer, Sigurjónsson was sent to the University of Copenhagen, where he joined a group of young intellectuals who looked to the Danish critic Georg Brandes (Brandes, Georg) and the philosophy of Friedrich Nietzsche (Nietzsche, Friedrich) for guidance. He soon concluded that the Icelandic language provided too small an audience for an ambitious dramatist and began to write his plays in both Icelandic and Danish.

After two unsuccessful plays came Fjalla-Eyvindur, which took Copenhagen by storm. Fjalla-Eyvindur is a dramatization of a popular Icelandic folktale of a wealthy young woman who gives up everything to join her outlaw lover, a sheep thief, in the hills. Sigurjónsson gave the story new life for the stage and wrote a final act that lifts it to great tragedy. Galdra-Loftur (1915; “Loftur the Sorcerer”; Eng. trans. Loftur: A Play), also based on a folktale, is about a student at the Cathedral School at Hólar who sells his soul to the devil. Sigurjónsson died prematurely of tuberculosis.