The famous physicist who developed the theory of relativity is Albert Einstein. He proposed the Special Theory of Relativity in 1905, which introduced groundbreaking concepts about the relationship between space and time, particularly regarding the constancy of the speed of light. Later, in 1915, he presented the General Theory of Relativity, which expanded upon these ideas to describe gravity as a curvature in spacetime caused by mass. Einstein’s work revolutionized theoretical physics and has had profound implications in cosmology and our understanding of the universe, making him one of the most influential scientists in history.