Network Information Theory is an advanced course designed for students who are interested in the quantitative aspects of information processing in a multi-terminal network setting. With the background of information theoretic results and tools in the point-to-point setup, questions regarding how to extend the framework beyond the simple point-to-point communication system naturally emerge soon after Claude E. Shannon's seminal paper in 1948. Research along this direction is collectively called Network Information Theory. In this course, based on the foundations developed in the preceding course Information Theory, we introduce representative results in this broad field, with applications in wireless communications, network information flow, distributed storage, etc..