Hermann von Siemens (9 August 1885 – 13 October 1986) was a German industrialist of the Siemens family.
He was the eldest son of Arnold von Siemens who himself was the eldest son of Werner von Siemens, the famous inventor and founder of Siemens & Halske, later to become the present-day Siemens AG. Hermann's mother Ellen, née von Helmholtz, was a daughter of Werner's close friend Hermann von Helmholtz, after whom his grandson was named. He was the eldest of five children.
After studying physical chemistry and becoming PhD, Hermann von Siemens started his career as an employee of the physical-chemical laboratory of Siemens & Halske, Berlin. In 1928 he became a member of the management board of Siemens & Halske. In 1929 he took over responsibility for the central laboratory of the company. He significantly contributed to the development of teleprinters. In 1935 he became member of the management board of a sister company, Siemens-Schuckertwerke AG. He also became a member of the supervisory boards of Vereinigte Stahlwerke, Mannesmann, Krupp and Deutsche Bank.
Before 1933 he was a member of the German National People's Party, a rival and opponent of Hitler's National Socialist German Workers' Party. From 1941 until 1946 he succeeded his uncle Carl Friedrich von Siemens as chairman of the Supervisory Boards of Siemens & Halske AG and Siemens-Schuckertwerke AG and thus became head of the German electrical and electronics company. As head of a company important for the production of war materials, the German government enqueued him among the "Wehrwirtschaftsführer". Siemens-Schuckert had to employ some skilled labor among deported people inside and outside of concentration camps. During the final years of World War II, numerous plants and factories in Berlin and other major cities were destroyed by Allied air raids. To prevent further losses, manufacturing was moved to alternative places and regions not affected by the air war. The goal was to secure continued production of important war-related and everyday goods. According to records, Siemens was operating almost 400 alternative or relocated manufacturing plants at the end of 1944 and in early 1945.