This text begins with an exposition of those aspects of tensor calculus and differential geometry needed for a proper exposition of the subject. The discussion then turns to the space-time of general relativity and to geodesic motion, comparisons and contrasts with Newton's theory being drawn where appropriate. A brief consideration of the field equations is followed by a discussion of physics in the vicinity of massive objects, including an elementary treatment of black holes. Particular attention is paid to those aspects of the theory that have observational consequences. The book concludes with brief introductory chapters on gravitational radiation and cosmology, and includes an appendix that reviews the special theory of relativity.