Emil Ketterer (6 August 1883 – 23 December 1959) was a German track and field athlete who competed in the 1912 Summer Olympics. Later in his life, he became an ardent Nazi and SA-Obergruppenführer. As a medical doctor, he was involved in approval and promotion of euthanasia under the Nazi regime. He was father-in-law of Hanns-Martin Schleyer, SS officer and victim of the Red Army Faction.
Born in Neustadt, he studied at the Ludwig Maximilian University of Munich, where he specialized in internal medicine and sports medicine. In 1912 Summer Olympics, he was eliminated in the first round of the 100 metres competition as he was not able to finish his race due to an injury.
He participated in World War I as a medical officer in the Bavarian army. After the war, Ketterer joined Bayerische Volkspartei and was involved in the Freikorps' clashes with left-wing radicals. As a member of the Reichskriegsflagge organisation, he took part in Hitler's Beer Hall Putsch, for which he was awarded the Nazi Blood Order, and in 1925 he became the NSDAP (Membership number 697). He joined SA in 1931 and was its Chief of Medical Services until 1937.
From 1933, Ketterer was a Munich City councillor. From 1936-1945, he was chairman of the TSV 1860 München sports club. He died in Munich.
His daughter Waltrude (1916-2008) was the wife of Hanns-Martin Schleyer, murdered by the RAF terrorists in 1977.