Social agents have been used in games often, for example, to create a social dimension (e.g. the inhabitants of a village) or to provide challenges to players (e.g. the opponents players face). These agents have an essential role in the players’ experience, and, as such, their creation needs to carefully considered. In this paper we propose a taxonomy of social roles that agents can play in games as a step towards the formalization of the problem of the creation of social agents in games. We believe that this taxonomy can help researchers to reach some common ground on the subject and, therefore, promote common views of the research problems involved in the design and development of social agents for games. We discuss several open challenges in the creation of social agents for games and discuss some future directions of research that can be grounded on the analysis of the taxonomy. For instance, many of the social roles proposed are played by agents that do not have much agency or autonomy. Also, there is a large number of under-explored social roles in games at the moment. The taxonomy serves as inspiration to guide game design involving social interactions with game actors, promoting new kinds of gameplay built on the interactive space afforded by the social agents.