Walter Buch (24 October 1883 in Bruchsal, Baden – 12 November 1949) was a German jurist, official in Nazi Germany and SS-Obergruppenführer. He was also Martin Bormann's father-in-law. After the end of the Second World War in Europe, Buch was classified as a major regime functionary or "Hauptschuldiger" in Denazification proceedings in 1949. On 12 November of that year, he committed suicide.
Born in Bruchsal, the son of a Senate President at the Baden High Court, Buch became a soldier in the First World War as a career officer. In 1918, he was released from the army as a major and then busied himself in the Baden Veterans' League.
By 1922, he had already become a member of the Nazi Party (NSDAP) and in August 1923 in Nuremberg became leader of the SA in Franconia. In mid 1923, after Hermann Ehrhardt on the one side and Ernst Röhm and Adolf Hitler on the other had fallen out with each other, the Stoßtrupp-Hitler ("Shock Troop-Hitler") was formed out of eight SA members for Hitler's protection. The Stoßtrupp was run by two former members of the Stabswache ("Staff Guard") who had also once belonged to the Brigade Ehrhardt. Julius Schreck founded the unit and the SS forerunner organization never numbered more than 20 members which included Buch. He thus found himself tied into the later SS and over time became an Honorary Leader of the SS ("Ehrenführer der SS ") with the rank of Obergruppenführer (under a new rank system brought in 1938, this became Stab Reichsführer SS).