The famous scientist who developed the theory of relativity is Albert Einstein. He introduced two theories: the special theory of relativity in 1905 and the general theory of relativity in 1915. The special theory revolutionized the understanding of space and time, proposing that the laws of physics are the same for all non-accelerating observers and that the speed of light in a vacuum is constant. The general theory of relativity expanded this by introducing gravity as a curvature of space-time caused by mass. Einstein's groundbreaking work has had profound implications in physics and has fundamentally changed the way we understand the universe.