The book "Functional Analysis" offers a comprehensive and easily understandable introduction to functional analysis, which is highly beneficial for both mathematicians and physicists. It covers not only the fundamental teaching content but also advanced topics such as the interpolation of linear operators and the Schwartz distribution theory. With over 200 exercises, many of which include detailed instructions or hints for solutions, it serves as a valuable reference work. Each chapter provides historical insights and further perspectives, while two appendices supply the necessary foundations for Lebesgue integrals as well as for metric and topological spaces. This completely revised new edition is ideal for mathematics and physics studies and serves as a solid basis for lectures.