The vaporization of a liquid for the purpose of concentrating a solution has long been in the domain of the chemical engineer and is a common operation in the chemical process industry. Purifying water via the evaporation route is not nearly as common as concentrating liquid solutions. Desalination by evaporation is a viable option, however, for two reasons. First, the operation is not affected by the salt concentration, and secondly, the salt concentration can easily be reduced via evaporation to concentrations below drinking water standards. This chapter provides a review of the basis and fundamentals of evaporation through classification of vaporizing equipment, describing equations, multiple-effect evaporation, thermocompression, other evaporation units, and desalination via the evaporation route. An application section provides three Illustrative Examples of evaporation concepts and implementation for desalination.