Albert Einstein is renowned for his theory of general relativity, which revolutionized our understanding of gravity and the fundamental forces of the universe. Published in 1915, this theory extended the principles of his earlier work on special relativity. General relativity describes gravity not as a force but as a curvature of spacetime caused by mass. This groundbreaking theory has had profound implications for cosmology, astrophysics, and our understanding of black holes and the expansion of the universe. Einstein's work has fundamentally shaped modern physics, earning him a lasting legacy as one of the greatest scientists in history.