Gerhard Ludwig Weinberg (born 1 January 1928) is a German-born American diplomatic and military historian noted for his studies in the history of Nazi Germany and World War II. Weinberg is the William Rand Kenan Jr. Professor Emeritus of History at the University of North Carolina at Chapel Hill. He has been a member of the history faculty at that institution since 1974. Previously he served on the faculties of the University of Michigan (1959–1974) and the University of Kentucky (1957–1959).

Weinberg was born in Hanover, Germany, and resided there the first ten years of his life. As Jews living in Nazi Germany, he and his family suffered increasing persecution. They emigrated in 1938, first to the United Kingdom and then in 1941 to New York State. Weinberg became a U.S. citizen, served in the U.S. Army during its Occupation of Japan in 1946–1947 and became a corporal. He returned to receive a BA (1948) in social studies from the New York State College for Teachers at Albany. He received his MA (1949) and PhD (1951) in history from the University of Chicago. Weinberg recounted some of his childhood memories and experiences in a two-hour long oral history interview for the United States Holocaust Memorial Museum.

Weinberg has studied the foreign policy of National Socialist Germany and the Second World War for his entire professional life. His doctoral dissertation (1951), directed by Hans Rothfels, was "German Relations with Russia, 1939–1941," subsequently published in 1954 as Germany and the Soviet Union, 1939–1941. From 1951 to 1954 Weinberg was a Research Analyst for the War Documentation Project at Columbia University and was Director of the American Historical Association Project for Microfilming Captured German Documents in 1956–1957. After joining the project to microfilm captured records at Alexandria, Virginia, in the 1950s, Weinberg published the Guide to Captured German Documents (1952).

In 1953–1954, Weinberg was involved in a scholarly debate with Hans-Günther Seraphim [de] and Andreas Hillgruber on the pages of the Vierteljahrshefte für Zeitgeschichte journal over the question of whether Operation Barbarossa, the German invasion of the Soviet Union in 1941, was a preventive war forced on Hitler by fears of an imminent Soviet attack. In a 1956 review of Hillgruber's book Hitler, König Carol und Marschall Antonescu, Weinberg accused Hillgruber of engaging at times in a pro-German apologia such as asserting that World War II began with the Anglo–French declarations of war against Germany on September 3, 1939, rather than the German invasion of Poland on September 1, 1939. In his 1980 monograph The Foreign Policy of Hitler's Germany Starting World War II 1937–1939, Weinberg noted that about the question of the war's origins that "my view is somewhat different" from Hillgruber's. In his 1981 book World in the Balance, Weinberg stated that "Hillgruber's interpretation is not, however, followed here". In his 1994 book A World At Arms, Weinberg called Hillgruber's thesis presented in his book Zweierlei Untergang – Die Zerschlagung des Deutschen Reiches und das Ende des europäischen Judentums (Two Kinds of Ruin – The Smashing of the German Reich and the End of European Jewry) "... a preposterous reversal of the realities". Weinberg sarcastically commented that if the German Army had held out longer against the Red Army in 1945 as Hillgruber had wished, the result would not have been the saving of more German lives as Hillgruber had claimed, but rather an American atomic bombing of Germany.

Another scholarly debate involving Weinberg occurred in 1962–1963 when Weinberg wrote a review of David Hoggan's 1961 book Der Erzwungene Krieg for the American Historical Review. The book claimed that the outbreak of war in 1939 had been due to an Anglo–Polish conspiracy against Germany. In his review, Weinberg suggested that Hoggan had probably engaged in forging documents (the charge was later confirmed). Weinberg noted that Hoggan's method comprised taking of all Hitler's "peace speeches" at face value, and simply ignoring evidence of German intentions for aggression such as the Hossbach Memorandum. Moreover, Weinberg noted that Hoggan often rearranged events in a chronology designed to support his thesis such as placing the Polish rejection of the German demand for the return of the Free City of Danzig (modern Gdańsk, Poland) to the Reich in October 1938 instead of in August 1939, thereby giving a false impression that the Polish refusal to consider changing the status of Danzig was due to British pressure.

Weinberg noted that Hoggan had appeared to engage in forgery by manufacturing documents and attributing statements that were not found in documents in the archives. As an example, Weinberg noted during a meeting between Neville Chamberlain and Adam von Trott zu Solz in June 1939, Hoggan had Chamberlain saying that the British guarantee of Polish independence given on March 31, 1939 "did not please him personally at all. He thereby gave the impression that Halifax was solely responsible for British policy". As Weinberg noted, what Chamberlain actually said was:

Do you [(vonTrott zu Solz)] believe that I undertook these commitments gladly? Hitler forced me into them!

Subsequently, both Hoggan and his mentor Harry Elmer Barnes wrote a series of letters to the American Historical Review protesting Weinberg's review and attempting to rebut his arguments. Weinberg in turn published letters rebutting Barnes's and Hoggan's claims.