Þórbergur Þórðarson (Thórbergur Thórdarson) (Hali í Suðursveit, 12 March 1888/1889[1] – Reykjavík, 12 November 1974) was an Icelandic author and Esperantist.

An ironist, satirist, volatile critic, and ground-breaking achiever in experimental auto-fiction, Þórbergur arguably remains among Iceland's most beloved 20th century authors.

As recounted in his largely autobiographical works, Íslenzkur aðall (1938) and Ofvitinn (1940), Þórbergur lived in poverty for much of his youth and early adulthood and could not afford secondary or higher education.

In January 1934, Þórbergur wrote a series of essays for the socialist daily Alþýðublaðið, titled "The Nazis' Sadistic Appetite" ("Kvalaþorsti nazista"[2]).

Iceland's public prosecutor filed charges against Þórðarson for supposedly offensive clauses in the article, one of which labelled Adolf Hitler "a sadist".

While only major work by Þórbergur are listed above he also wrote a number of essays and other pieces on a variety of subjects, besides writing in the international language of Esperanto.