This Element presents the philosophy of special relativity: from the foundations of the theory in Newtonian mechanics, through its birth out of the ashes of 19th Century ether theory, through the various conceptual paradoxes which the theory presents, and finally arriving at some of its connections with Einstein's later theory of general relativity. It illustrates concepts such as inertial frames, force-free motion, and dynamical versus geometrical understandings of physics, the standard hierarchy of classical spacetimes, the concept of a symmetry of a physical theory, Poincaré invariant, Einstein's 1905 derivation of the Lorentz transformations, spacetime structure from Aristotle to Minkowski, general covariance, dynamical and geometrical approaches to spacetime, the conventionality of simultaneity, Frame-dependent effects, and the twin paradox.