The chapter introduces the platform types designed for supporting the tower, nacelle and turbine assembly of floating offshore wind turbines. Basic information on hydrodynamics is presented to provide an understanding of platform behaviour in waves. The classification method that distinguishes the platform types is stabilization. Covering this topic, buoyancy, mooring and ballast stabilized platform types are illustrated and briefly explained. The advantages and disadvantages of each approach are considered and summarized. The areas in which the benefits of each type are the most evident are clarified through various comparative studies. Most platform models are currently still at demonstration or conceptual stages. For this reason, computer codes that aim to capture their motions become particularly significant in design stages, and they are discussed next. A significant number of projects at the initial stages of planning and application are being developed in Japan, Europe and the United States. The platform types observed in these projects are presented. The chapter concludes with newly evolving design standards and a brief discussion on the optimization of platform shapes.