The present book, the result of thirty years of experience in Astrophysics and the strategies used to solve the problems that its teaching entails, comes to fill the enormous gap that exists in this type of publication in the Spanish language. Its purpose is not to serve as an introduction to Astronomy, but rather to deepen the knowledge of some of the most fascinating aspects of our Universe: stars and galaxies, hence its title. And it is that although it is a book of a university nature, linked to the contents that are currently taught, it is also open to other readers interested in the subject who will be able to follow the text, skipping, when necessary, the mathematical formulation and relying on numerous figures and graphics that accompany the explanations. The book is made up of nineteen chapters grouped into three blocks - plus a historical introduction and a glossary - presented in direct and simple language that provides both rigorous and accessible content on the fundamental notions of stellar, galactic and extragalactic astrophysics. An exceptional compendium that will allow the reader to create a vision of the Universe in which we live.