Introduction to Coding Theory introduces coding theory and its main areas of application. The author's approach is gentle, with sections devoted to basic concepts such as congruences and fields of prime order, thus making the treatment accessible to a wide audience. All chapters are accompanied by a problems section, with a total of over 300 exercises in the book. The end point of the theoretical development is a complete introduction to cyclic codes, a discussion of the theory of finite fields, and an introduction to the geometric description of linear codes as multisets of points in projective spaces. A solutions manual is available with qualifying course adoptions.