The primary contribution of Albert Einstein to modern physics is the formulation of the theory of relativity, specifically his equation E=mc², which describes the equivalence of mass and energy. This groundbreaking theory revolutionized the understanding of space, time, and gravity. Einstein's insights led to advancements in various fields, including cosmology and quantum mechanics. His work has deeply influenced both theoretical and practical applications in science, contributing to innovations in technology and our understanding of the universe, making him one of the most prominent figures in scientific history.