The book presents, in a condensed form, all aspects of special relativity (Part I) and relativistic gravitation (Part II). The emphasis is on physical experiment, observation and interpretation. The first four chapters in Part I introduce special relativity, the following three chapters deal with mathematical derivation and introduce new concepts as background for Part II. Part II describes Newtonian gravitation using metric theory (placing it in general relativity); experimental tests are described using the post-Newtonian parameters; the Newtonian and relativistic cosmologies are presented. The following three chapters contain detailed discussion of general relativity with different geometries introducing their effect. The last chapter presents two practical projects: the satellite gyroscope to measure the gravitational interactions spin-orbit and spin-spin, and a gravitational wave detector. The author provides a rigorous theoretical treatment, at a level suitable for advanced undergraduates and beginning graduate students.