The famous scientist known for developing the theory of relativity was Albert Einstein. He introduced the special theory of relativity in 1905 and later the general theory in 1915. His theories revolutionized our understanding of physics, particularly concepts of time, space, and gravity. The famous equation E=mc², which describes the relationship between mass and energy, became a cornerstone of modern physics and has had profound implications in various scientific fields, including cosmology and quantum mechanics. Einstein's work fundamentally altered how we perceive the universe and laid the groundwork for future scientific advancements.