Robert Max Wasilii Kempner (17 October 1899 – 15 August 1993) was a German lawyer of Jewish descent who played a prominent role during the Weimar Republic and who later served as assistant U.S. chief counsel during the International Military Tribunal at Nuremberg.

He was the son of Walter Kempner and Lydia Rabinowitsch-Kempner, who were both microbiologists and regarded as one of the prominent scientist couples of their time.

[3] After finishing his studies Kempner became a successful lawyer in Berlin during the 1920s, and then advanced to chief legal advisor to the Prussian police in 1928.

[2] After World War II Kempner returned to Germany, the land of his birth, to serve as assistant U.S. chief counsel during the International Military Tribunal at Nuremberg.

Kempner also served as counsel at the 1947–1948 trial of the German Foreign Office and is credited with finding the text of the Wannsee Protocol, a critical historical document in the history of the Holocaust.

[7] Most significant among this historic cache was the diary of Alfred Rosenberg, one of Hitler's most long-standing leading supporters, who had been convicted and hanged for his war crimes in 1946.

The loose-leaf diary pages, dating from 1936 through 1944, passed through various hands after Kempner's death at age 93 in 1993, until they were reported to have been finally recovered by U.S. ICE agents in June 2013.