Carl Wilhelm Wagner (May 25, 1901 – December 10, 1977) was a German Physical chemist. He is best known for his pioneering work on Solid-state chemistry, where his work on oxidation rate theory, counter diffusion of ions and defect chemistry led to a better understanding of how reactions take place at the atomic level. His life and achievements were honoured in a Solid State Ionics symposium commemorating his 100th birthday in 2001, where he was described as the Father of Solid State Chemistry.