S. R. Srinivasa Varadhan, also known as Sathamangalam Ranga Iyengar Srinivasa Varadhan, is an Indian-American mathematician renowned for his significant contributions to the field of probability theory and mathematical statistics. He was born on January 2, 1940, in Chennai, India. Varadhan's work is highly regarded for its profound impact on stochastic processes and their applications in various areas, including statistical physics, partial differential equations, and random media. He is particularly known for his groundbreaking work on large deviation theory, which deals with the study of extremely rare events in probability distributions. His research has provided crucial insights into the behavior of complex systems and has found applications in diverse fields, such as physics, biology, finance, and engineering.