The famous physicist known for his mass-energy equivalence formula is Albert Einstein. He developed the formula E=mc², which established a relationship between mass (m) and energy (E), showing that mass can be converted into energy and vice versa. This groundbreaking equation is a cornerstone of modern physics, profoundly impacting our understanding of the universe. Einstein's theories of relativity, including both special and general relativity, have reshaped theories about time, space, and gravity. His work laid the groundwork for advancements in numerous fields, including cosmology and nuclear physics.