Ari Þorgilsson (1067/1068 – 9 November 1148; Old Norse: [ˈɑre ˈθorˌɡilsˌson]; Modern Icelandic: [ˈaːrɪ ˈθɔrˌcɪlsˌsɔːn]; also anglicized Ari Thorgilsson) was Iceland's most prominent medieval chronicler. He was the author of Íslendingabók, which details the histories of the various families who settled Iceland. He is typically referred to as Ari the Wise (Ari fróði), and according to Snorri Sturluson was the first to write history in Old Norse.
Ari was a part of the Haukdælir family clan and studied in the school in Haukadalur as a student of Teitur Ísleifsson (the son of Ísleifur Gissurarson, first bishop of Iceland). There he became acquainted with Classical education. His writings clearly indicate that he was familiar with Latin chronicler traditions, but at the same time he is widely regarded as excelling in the Icelandic oral storytelling tradition.