Mean Field Games and Mean Field Type Control Theory Introduction General Presentation of Mean Field Control Problems Discussion of the Mean Field game Discussion of the Mean Field Type Control Approximation of Nash Games with a large number of players Linear Quadratic Models Stationary Problems Different Populations Nash differential games with Mean Field effect. Mean field games and Mean field type control introduce new problems in Control Theory. The terminology “games” may be confusing. In fact they are control problems in the sense that one is interested in a single decision maker whom we can call the representative agent. However these problems are not standard since both the evolution of the state and the objective functional is influenced but terms which are not directly related to the state or the control of the decision maker. They are however indirectly related to him in the sense that they model a very large community of agents similar to the representative agent. All the agents behave similarly and impact the representative agent. However because of the large number an aggregation effect takes place. The interesting consequence is that the impact of the community can be modeled by a mean field term but when this is done the problem is reduced to a control problem. .