Sidney Bradshaw Fay (13 April 1876 in Washington, D.C. – 29 August 1967 in Lexington, Massachusetts) was an American historian, whose examination of the causes of World War I, The Origins of the World War (1928; revised edition 1930) remains a classic study. In this book, which won him the George Louis Beer Prize of the American Historical Association, Fay claimed that Germany was too readily blamed for the war and that a great deal of the responsibility instead rested with the Allies, especially Russia and Serbia. His stance is supported by several modern-day scholars, such as Christopher Clark, though it remains controversial. Fay left Harvard University (Ph.D. 1900) to study at the Sorbonne and the University of Berlin. He taught at Dartmouth College (1902–14) and Smith College (1914–29) and, after the publication of his major book, at both Harvard and Yale University.
Fay's conclusion was that all the European powers shared in the blame, but most of all the system of secret alliances that divided Europe after the Franco-Prussian War into two mutually suspicious camps of group solidarity, Triple Alliance against Triple Entente (Fay's student Allan B. Calhamer, would later develop and publish the game Diplomacy, based on this thesis) but that Austro-Hungary, Serbia and Russia were primarily responsible for the immediate cause of war's outbreak. Other forces besides militarism and nationalism were at work: the economics of imperialism and the newspaper press played roles.