This textbook introduces all teaching-relevant topics of elementary geometry. It is suitable as a companion book to the lecture of the same name for students in mathematics education, both in Bachelor and state examination programs. The last two chapters are suitable for advanced courses and provide many possible topics for seminar and research papers. The 4th edition has been carefully revised and expanded. Some topic complexes are now presented in more detail. Additional illustrations of geometric models have been included, and the number of exercises has been further increased. At the end of the book, readers will find solutions to selected problems from all chapters; thus, the book is very well suited for exam preparation. The authors also offer a special service: any student who needs assistance with solving the exercises can contact the authors.