This text presents a graduate-level introduction to differential geometry for mathematics & physics students The exposition follows the historical development of the concepts of connection & curvature with the goal of explaining the Chern-Weil theory of characteristic classes on a principal bundle Along the way we encounter some of the high points in the history of differential geometry for example Gauss' Theorema Egregium & the Gauss-Bonnet theorem Exercises throughout the book test the reader's understanding of the material & sometimes illustrate extensions of the theory Initially the prerequisites for the reader include a passing familiarity with manifolds After the first chapter it becomes necessary to understand & manipulate differential forms A knowledge of de Rham cohomology is required for the last third of the text Prerequisite material is contained in author's text An Introduction to Manifolds & can be learned in one semester For the benefit of the reader & to establish common notations Appendix A recalls the basics of manifold theory in addition in an attempt to make the exposition more self-contained sections on algebraic constructions such as the tensor product & the exterior power are included Differential geometry as its name implies is the study of geometry using differential calculus It dates back to Newton & Leibniz in the seventeenth century but it was not until the nineteenth century with the work of Gauss on surfaces & Riemann on the curvature tensor that differential geometry flourished & its modern foundation was laid Over the past one hundred years differential geometry has proven indispensable to an understanding of the physical world in Einstein's general theory of relativity in the theory of gravitation in gauge theory & now in string theory Differential geometry is also useful in topology several complex variables algebraic geometry complex manifolds & dynamical systems among other fields The field has even found applications to group theory as in Gromov's work & to probability theory as in Diaconis's work It is not too far-fetched to argue that differential geometry should be in every mathematician's arsenal