Dušan Třeštík (1 August 1933, Sobědruhy u Teplic, Czechoslovakia – 23 August 2007, Prague) was a Czech historian. He specialized in medieval history (Dark Ages (500–1000)) of the Czech lands and theory of history.
Třeštík studied history at the Charles University in 1951–1956 where his tutor was František Graus. After two years at the Charles University, since 1958 he worked in the Historic Institute of the Academy of Science and Arts. In last years he was prominent in its Centre of Medievial Studies. In 1959 he married historian Barbara Krzemieńska and in 1968 he studied in West Germany and France. Třeštík was a stark defender of veracity Kristián's legend. As a theorist of history he criticised neopositivist approach of the Czech scholarship history mainstream and its icon Josef Pekař. He labeled it as faktopis.
Since 1989 he also published a lot of political texts (collected as Češi. Jejich národ, stát, dějiny a pravdy v transformaci, 1999), especially in Lidové Noviny (from 1993 to 1996 he was a member of its editorial board) and Mladá Fronta Dnes. He criticised Sudeten Germans, but he joined Impuls 99 despite being close to Václav Klaus. After 9/11 Třeštík was sceptical towards neoconservative politics and invasion to Iraq.