The Golden Age of Theoretical Physics contains 34 essays on the quantum and relativity theories and their applications. Most of them were presented as lectures at various universities in Europe and the USA by Jagdish Mehra, while some were published individually and others in collaboration with Helmut Rechenberg. This book deals with the most important themes developed in the first 40 years of the 20th century by some of the greatest pioneers and architects of modern physics. It is a vital source of information about what can be described as "the golden age of theoretical physics".