Cancer is an evolutionary disease where, although mutations are thought to be random, selection clearly is not. Selection is driven by the interactions between the different types of tumor cells, other cells in the tumor microenvironment and the physical microenvironment itself. Game Theory in general and Evolutionary Game Theory in particular are mathematical frameworks in which to investigate the role of the interactions between cells with different phenotypes and traits in the evolutionary dynamics of a tumor. In this presentation I will introduce the history of Game Theory, some canonical games and then proceed to describe how it has been used to model cancer, the advantages of the approach and some shortcomings.