Karl Imhoff (7 April 1876 in Mannheim – 28 September 1965) was a German civil engineer, author, and a pioneer of wastewater treatment used throughout the world.

Karl Imhoff was the driving force in the development and invention of the technical apparatuses and methods of sewage treatment (the trickling - and activated sludge process).

Imhoff provided not only significant technical innovations, but also design rules derived from experience in the operation of sewage treatment plants.

Imhoff was awarded honorary degrees by the Institutes of Technology in Karlsruhe, Stuttgart and Aachen and, in 1953, the Great Cross of Merit of the Federal Republic of Germany and in 1959 the "Bunsen Pettenkofer honor roll".

This is awarded to individuals who have made in an excellent way to promote water and wastewater management in scientific or practical way by the Deutscher Verein des Gas- und Wasserfaches.