Chemical looping is an important new class of technologies, which can be deployed for direct combustion, as well as being used in reforming applications. In this type of system, a solid carrier is used to bring oxygen to the fuel gas, so that it can be subsequently released as a pure CO2 stream suitable for use, or more likely sequestration or storage. The solid is then regenerated in a reactor using air, so that the technology effectively achieves oxygen separation from air without the use of a costly cryogenic process or membrane technology. This chapter will restrict itself to considering the uses of solid carriers only and more specifically those in which oxygen is transported, and not CO2 as is the case for Calcium Looping. Particular focuses of this chapter will be on the use of this technology for syngas and H2 production, gasification, and reforming as well as its use with solid fuels. Another issue that will be discussed is high-pressure cycles, which are ultimately necessary if such systems are to be integrated into high efficiency heat, steam, and power cycles.