This textbook provides a comprehensive and lucid modern introduction to galaxies for advanced undergraduate students in astronomy and physics. Basic astrophysics, multiwavelength observations, and theoretical concepts are carefully combined to develop a thorough and integrated understanding. The necessary background astronomy is included, and mathematics has been kept to the minimum required to enable the student to grasp the essence of a calculation, or the basis for a method. Techniques for observation and measurement are also clearly explained, with a critical review of their limits and accuracy. Starting from the basic properties of stars, we explore our own Milky Way, and work outwards to look at young galaxies in the very distant Universe. We examine galaxies in their environments, including groups and clusters. We are shown how the shapes of galaxies, the orbits of their stars, and the abundance and distribution of heavy elements, all give clues to how galaxies form. Throughout we see how galaxies are observed across the electromagnetic spectrum, and how the results can be synthesized into a coherent picture. Exciting topics such as gravitational lensing, dark matter, and galactic collisions and mergers are also covered. The clear and friendly style of the text thorough coverage of fundamentals, extensive use of up-to-date observations, and helpful problems make this an ideal introduction to galaxies and an excellent preparation for more advanced texts and the research literature. The most up-to-date and comprehensive undergraduate textbook on galaxies available ; requires only basic undergraduate physics and mathematics and no prior knowledge of astronomy ; provides an integrated and thoroughly modern approach to the subject, combining basic astrophysics, multiwavelength observations, and theoretical concepts ; covers techniques for observation and measurement, and a critical review of their limits and accuracy ; extensively illustrated with up-to-date observations ; provides a thorough grounding of the fundamentals and prepares students for more advanced text and research literature.