Walter Kohn (born March 9,1923 in Vienna, Austria) is an Austrian-born American physicist who was awarded, with John A. Pople, the Nobel Prize in chemistry in 1998. The award recognized their contributions to the understandings of the electronic properties of materials. In particular, Kohn played a leading role in the development of the density-functional theory, which made it possible to incorporate quantum mechanical effects in the electronic density (rather than through its many-body wavefunction). This computational simplification led to many insights and became an essential tool for electronic materials, atomic and molecular structure.