In theoretical chemistry and molecular physics, Coulson-Fischer theory provides a quantum mechanical description of the electronic structure of molecules. The 1949 seminal work of Coulson and Fischer[1] established a theory of molecular electronic structure which combines the strengths of the two rival theories which emerged soon after the advent of quantum chemistry - valence bond theory and molecular orbital theory, whilst avoiding many of their weaknesses. For example, unlike the widely used Hartree-Fock molecular orbital method, Coulson-Fischer theory provides a qualitatively correct description of molecular dissociative processes.[2] The Coulson-Fischer wave function has been said to provide a third way in quantum chemistry.[3] Modern valence bond theory is often seen as an extension of the Coulson-Fischer method. For a single two-electron bond, the Coulson-Fischer theory is equivalent to the Generalized valence bond method.