Using fundamental physics, the theory of stellar structure and evolution is able to predict how stars are born, how their complex internal structure changes, what nuclear fuel they burn, and what their ultimate fate is - a fading whitedwarf, or a cataclysmic explosion as a supernova, leaving behind a collapsed neutron star or black hole. This lucid textbook provides students with a clear and pedagogical introduction to the theory of stellar structure and evolution. It requires only basic physics and mathematics learnt in first- and second-year undergraduate studies, and assumes no prior knowledge of astronomy. The unique feature of this book is the emphasis throughout on the basic physical principles governing stellar evolution. Exercises and their full solutions are included to help students test their understanding. This textbook provides a stimulating introduction for undergraduates in astronomy, physics, planetary science and applied mathematics taking a course on the physics of stars.