Harnack is a surname and may refer to: Adolf von Harnack (1851-1930), German liberal theologian and historian of religion Arvid Harnack (1901-1942), anti-Nazi resistance fighter Ernst von Harnack (1888-1945), anti-Nazi resistance fighter Mildred Harnack (1902-1943), anti-Nazi resistance fighter Theodosius Harnack (1817-1889), theologian Harnack's principle… (More on Harnack)