The purpose of this chapter is to introduce an overall classification system for Serious Games. ?The intention of this classification is to guide people through the vast field of Serious Games by providing them with a general overview. For example, it may appeal to teachers who wish to find games with strong educational potential though they may be outside the “edugames” field. This chapter will start by discussing the definition of Serious Games, and define them as having a combination of “serious” and “game” aspects. This theoretical framework will be used to review previous classification systems and discuss their limitations. It will then introduce a new classification that addresses a number of these limitations: the G/P/S model. This classifies games according to both their “serious-related” and “game-related” characteristics, and combines the strengths of several previous classification systems.