Hans Mommsen (5 November 1930 – 5 November 2015) was a German historian, known for his studies in German social history, for his functionalist interpretation of the Third Reich, and especially for arguing that Adolf Hitler was a weak dictator. Descended from Nobel Prize-winning historian Theodor Mommsen, he was a member of the Social Democratic Party of Germany.
 Mommsen was born in Marburg, the child of the historian Wilhelm Mommsen and great-grandson of the historian of Rome Theodor Mommsen. He was the twin brother of historian Wolfgang Mommsen. He studied German, history and philosophy at the University of Heidelberg, the University of Tübingen and the University of Marburg. Mommsen served as professor at Tübingen (1960–1961), Heidelberg (1963–1968) and at the University of Bochum (since 1968). He married Margaretha Reindel in 1966. He was a member of the Social Democratic Party of Germany from 1960 until his death. He died on 5 November 2015, his 85th birthday.
 Much of Mommsen's early work concerned the history of the German working class, both as an object of study itself and as a factor in the larger German society. Mommsen's 1979 book, Arbeiterbewegung und nationale Frage (The Labour Movement and the National Question), a collection of his essays written in the 1960s–70s was the conclusion of his studies in German working class history.
 Mommsen was a leading expert on Nazi Germany and the Holocaust. He was a functionalist in regard to the origins of the Holocaust, seeing the Final Solution as a result of the "cumulative radicalization" of the German state as opposed to a long-term plan on the part of Adolf Hitler.
 Mommsen is best known for arguing that Hitler was a "weak dictator" who rather than acting decisively, reacted to various social pressures. Mommsen believed that Nazi Germany was not a totalitarian state. Together with his friend Martin Broszat, Mommsen developed the structuralist interpretation of the Third Reich, that saw the Nazi state as a chaotic collection of rival bureaucracies engaged in endless power struggles.
 In regards to the debate about foreign policy, Mommsen has argued that German foreign policy did not follow a "programme" during the Nazi era, but was instead "expansion without object" as the foreign policy of the Reich driven by powerful internal forces sought expansion in all directions.
 Mommsen has faced criticism in the following areas:
 In the Historikerstreit debate about how to incorporate the Holocaust into German historiography, Mommsen argued that the Holocaust and fascist crimes could not be equated with Soviet crimes. Mommsen argued that the growth in pacifist feeling in the Federal Republic as reflected in widespread public opposition to the American raid on Libya in April 1986 made it imperative for the Americans and the West German government to promote a more nationalistic version of German history, and that was what was behind the Historikerstreit.
 Mommsen has written highly regarded books and essays on the fall of the Weimar Republic, blaming the downfall of the Republic on German conservatives. Like his brother Wolfgang, Mommsen was a champion of the Sonderweg (Special Path) interpretation of German history that sees the ways German society, culture and politics developed in the 19th century as having made the emergence of Nazi Germany in the 20th century virtually inevitable.[citation needed]
 Another area of interest for Mommsen is dissent, opposition and resistance in the Third Reich. Much of Mommsen's work in this area concerns the problems of "resistance without the people". Mommsen has drawn unfavorable comparisons between what he sees as conservative opposition and Social Democratic and Communist resistance to the Nazis. Mommsen was an expert on social history and often writes about working-class life in the Weimar and Nazi eras.
 Starting in the 1960s, Mommsen was one of a younger generation of West German historians who provide a more critical assessment of Widerstand within German elites, and came to decry the "monumentalization" typical of German historical writing about Widerstand in the 1950s. In two articles published in 1966, Mommsen proved as false the claim often advanced in the 1950s that the ideas behind "men of July 20" were the inspiration for the 1949 Basic Law of the Federal Republic.
 During the "Goldhagen Controversy" of 1996, Mommsen emerged as one of Daniel Goldhagen's leading opponents, and often debated Goldhagen on German TV. Mommsen's friend, the British historian Sir Ian Kershaw wrote he thought that Mommsen had "destroyed" Goldhagen during their debates over Goldhagen's book Hitler's Willing Executioners.
 In an August 2000 book review, Mommsen called Norman Finkelstein's book The Holocaust Industry "a most trivial book, which appeals to easily aroused anti-Semitic prejudices."
 A major figure in Germany, Mommsen often took stands on the great issues of the day, believing that the responsibility for ensuring the mistakes of the past are never repeated rests upon an engaged and historically-conscious citizenry. Mommsen saw it as the duty of the historian to constantly critique contemporary society.