This textbook provides a didactic introduction to the topic of group theory in physics, with a special focus on solid state physics issues. The book is useful for students who encounter such problems in their first scientific work (in theory or experiment). In addition to the basic introduction to group theory and representation theory, the book deals with point groups, double point groups, and space groups, which are essential in solid state physics. As an example for systems with space group symmetry, electrons in periodic potentials are discussed. Furthermore, there are chapters on material tensors and the Wigner Eckart theorem for the evaluation of matrix elements. The latter is especially interesting for students dealing with spectroscopic problems. The content is accompanied by a series of exercises and examples. A set of solutions can be found in the appendix.