 Albert Einstein (1879–1955) is well known as the most prominent physicist of the twentieth century. His contributions to twentieth-century philosophy of science, though of comparable importance, are less well known. Einstein’s own philosophy of science is an original synthesis of elements drawn from sources as diverse as neo-Kantianism, conventionalism, and logical empiricism, its distinctive feature being its novel blending of realism with a holist, underdeterminationist form of conventionalism. Of special note is the manner in which Einstein’s philosophical thinking was driven by and contributed to the solution of problems first encountered in his work in physics. Equally significant are Einstein’s relations with and influence on other prominent twentieth-century philosophers of science, including Moritz Schlick, Hans Reichenbach, Ernst Cassirer, Philipp Frank, Henri Bergson, Émile Meyerson.