Special Relativity, introduced by Albert Einstein in 1905, fundamentally transformed our understanding of space, time, motion and energy. It is based on two central principles: the laws of physics are the same in all inertial reference frames, and the speed of light in a vacuum is constant for all inertial observers, regardless of their relative motion. These seemingly innocuous principles lead to some remarkable consequences, including time dilation, length contraction and the relativity of simultaneity. Events that occur simultaneously for one observer need not be simultaneous for another, while moving clocks are measured to run slower and moving objects shorter along their direction of motion. The mathematical framework underlying these phenomena is provided by the Lorentz transformations, which replace the Galilean transformations of classical mechanics. Special Relativity also establishes a new relationship between energy and momentum, encapsulated in the famous equation $E^2=p^2c^2+m^2c^4$, with $E=mc^2$ as the special case for an object at rest with momentum $p=0$. Far from being merely a theoretical curiosity, the theory has profound practical consequences, finding applications in particle accelerators, nuclear physics and the operation of GPS satellites. It also provides the foundation for understanding the relationship between space and time as a unified four-dimensional spacetime. Special Relativity is therefore not simply a correction to Newtonian mechanics at high speeds, but a profound re-examination of some of our most fundamental assumptions about the physical universe.