Centrifugal compressors are widely used to compress gas in industrial 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 and their operational characteristics are explained. We will also discuss the components of centrifugal compressors required to make the compressor function. The third part of this short course will give an overview of different drivers for centrifugal gas compressors, including gas turbines and electric motors of various configurations. We will focus particularly on the interaction between the driver characteristics and the compressor and system characteristics.