Friedrich Wilhelm Georg Kohlrausch (14 October 1840 – 17 January 1910) was a German physicist who investigated the conductive properties of electrolytes and contributed to knowledge of their behaviour.

His early work helped to extend the absolute system of Carl Friedrich Gauss and Wilhelm Weber to include electrical and magnetic measuring units.

First, the experiments from which he deduced his law of independent migration of ions became canonical and disseminated from Kohlrausch's laboratories in Göttingen, Zürich, and Darmstadt; Svante Arrhenius, Wilhelm Ostwald and Jacobus Henricus van 't Hoff, the original Ionists, all trained with methods and equipment of Kohlrauschian lineage.

He used alternating current to prevent the formation of electrolysis products (H2 and O2 gas evolution, or metal deposition); this enabled him to obtain very precise results.

During 1895 he succeeded Hermann von Helmholtz as President of the Physikalisch-Technische Reichsanstalt (PTR – Imperial Physical Technical Institute), an office which he held until 1905.

Kohlrausch was intent on creating optimum working conditions in the laboratories and to shield the labs from unwanted external influences.

However, before the streetcar was to make its first journey, the institute succeeded in developing an astatic torsion magnetometer which was uninfluenced by disturbing electromagnetic fields.

The use of this instrument and the shielded wire galvanometer developed by du Bois and Rubens meant that precision electrical and magnetic work continued to be possible.

This is attributable, above all, to the detailed descriptions provided of the measuring methods that form the basis of technical and experimental applications in many fields in physics.

Kohlrausch was also the author of Ueber den absoluten Leitungswiderstand des Quecksilbers (On the electrical resistance of mercury, 1888), and of many papers contributed to the Annalen der Physik und Chemie, and other scientific journals.