My Opposition (German: Mein Widerstand) is a diary secretly written by the German social democrat Friedrich Kellner (1885–1970) during World War II to describe life under Nazi Germany and to expose the propaganda and the crimes of the Nazi dictatorship. It is considered one of the most comprehensive diaries of the period. The first entry in the 861-page diary is dated September 13, 1939, and the last entry is May 17, 1945.