This textbook presents the topics typically covered in a standard lecture on discrete structures. It is aimed at students of computer science and mathematics (teaching degree and bachelor/master) and is designed as a companion for lectures, for self-study, and for exam preparation. Numerous exercises facilitate the deepening of the learning material. With its compact presentation of all important discrete and algebraic structures and its extensive index, the book also serves as a reference work for mathematicians, computer scientists, and natural scientists. Contents: From propositional and predicate logic to sets and combinatorics, numbers, relations and mappings, graphs, and a rich spectrum of algebraic structures, along with a brief insight into category theory. The 2nd edition is complete.