Carl Wilhelm Wagner (25 May 1901 &ndash; 10 December 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.