The Special Theory of Relativity, proposed by Albert Einstein in 1905 and enriched by many contemporary physicists, revolutionized our understanding of space, time, energy, and motion. This becomes an essential tool while dealing with subatomic particles in high-energy physics, where the speeds of the particles reach near the speed of light. This chapter provides a comprehensive introduction to the fundamental principles and mathematical framework of the special theory of relativity. It starts with the classical Galilean relativity, showing explicitly the non-invariance of the speed of light under Galilean transformation, while outlining other inadequacies. Then it discussed the electromagnetic waves and speed of light, before setting the stage to introduce the postulates of the special theory of relativity. The derivation of Lorentz transformations is presented, highlighting their interpretation as hyperbolic rotations in Minkowski spacetime. Essential consequences such as time dilation, length contraction, relativity of simultaneity, velocity addition, relativistic Doppler effect, and the upper limit of possible speeds are discussed in detail.