This book presents an introduction into Robinson's nonstandard analysis, which is an application of model theory in analysis. Unlike some texts, it does not attempt to teach elementary calculus on the basis of nonstandard analysis, but points to some applications in more advanced analysis. These can hardly be obtained by standard methods such as a deeper investigation of Hahn-Banach limits or of finitely additive measures. The contents move from a discussion of the preliminaries to Nonstandard Models; Nonstandard Real Analysis; Enlargements and Saturated Models; Functionals, Generalized Limits, and Additive Measures; and finally Nonstandard Topology and Functional Analysis. The reader is not expected to have any background in model theory; some background in analysis, topology, or functional analysis is useful - although the book is as much self-contained as possible and can be understood after a basic calculus course.