Richard Wilhelm Heinrich Abegg (9 January 1869 – 3 April 1910) was a German chemist[4] and pioneer of valence theory.

Abegg received his PhD on 19 July 1891 as the student of August Wilhelm von Hofmann at the University of Berlin.

Abegg discovered the theory of freezing-point depression and anticipated Gilbert Newton Lewis's octet rule by revealing that the lowest and highest oxidation states of elements often differ by eight.

He researched many topics in physical chemistry, including freezing points, the dielectric constant of ice, osmotic pressures, oxidation potentials, and complex ions.

He then attended the University of Berlin, from which he received his doctorate as the student of August Wilhelm von Hofmann.

Clara Immerwahr, the first wife of Fritz Haber, studied and graduated as his student.

Abegg is known best for his research recognizing the role that valence had with respect to chemical interactions.