This is the first biography ever written on the distinguished physicist Julian Schwinger. Schwinger was one of the most important and influential scientists of the twentieth century. The list of his contributions is staggering, from his early work leading to the Schwinger action principle, Euclidean quantum field theory, and the genesis of the standard model, to later valuable work on magnetic charge and the Casimir effect. He also shared the 1965 Nobel Prize in Physics with Richard Feynman. However, even among physicists, understanding and recognition of his work remains limited. This book by Mehra and Milton, both of whom were personally acquainted with Schwinger, presents a unique portrait that sheds light on both his personality and his work through discussion of his lasting influence on science. Anyone who wishes to gain a deeper understanding of one of the great physicists of this century needs to read this book.