The book presents, in a condensed form, all aspects of special relativity and relativistic gravitation. 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.