This is the first of two volumes introducing structural and continuum mechanics in a comprehensive and consistent way. The current book presents all theoretical developments both in text and by means of an extensive set of figures. This same approach is used in the many examples, drawings and problems. Both formal and intuitive (engineering) arguments are used in parallel to derive the principles used, for instance in bending moment diagrams and shear force diagrams. A very important aspect of this book is the straightforward and consistent sign convention, based on the stress definitions of continuum mechanics. The book is suitable for self-education.