This textbook provides a clear introduction to the theory and application of nonlinear systems and controls. The author explains the methods of nonlinear control, which are known from control theory research and are becoming increasingly important in industrial applications. The fundamentals of nonlinear dynamics, stability theory, controllability, nonlinear control of linear and nonlinear systems, and nonlinear state transformations are covered. Furthermore, the concepts of observability and the theory and application of nonlinear observers are described. The main features of the book are the comprehensive presentation of the theory, excellent comprehensibility, many example applications, and more than a hundred exercises with solutions, which are illustrated by numerous color diagrams. This book is aimed at advanced engineering students and engineers in industry.