Centrifugal Compressors are widely used to compress gas in oil and gas applications. This short course will address the general principles of gas compression, and explain the theory behind the concepts of compressibility, head, and efficiency. Also, the importance of the interaction between the compressor, and the system will be discussed. In a second part, the working principles of centrifugal compressors, their operational characteristics and their interaction with the system are explained. We will also discuss the components of centrifugal compressors required to make the compressor function and drivers for centrifugal compressors. The third part is dedicated to hands on examples on how to use the information given in part 1 and 2 to size compressors, evaluate compressor test data, and trouble shoot compressor performance issues.