This book provides an incisive, self-contained introduction to one of the most intriguing subjects in modern physics, presenting the evidence we have from astrophysics for the existence of dark matter, the theories for what it could be, and the cutting-edge experimental and observational methods for testing them. It begins with a survey of the astrophysical phenomena, from rotation curves to lensing and cosmological structure formation. It goes on to offer the most comprehensive overview available of all three major theories, discussing weakly interacting massive particles {WIMPs}, axions, and primordial black holes. The book explains the constraints on each theory, such as direct detection and indirect astrophysical limits, and enables students to build physical intuition using hands-on exercises and supplemental material. The only book to treat extensively WIMPs, axions, and primordial black holes, Provides balanced coverage of the evidence, theory, and testing for dark matter from astrophysics, particle physics, and experimental physics, Includes original problems and short quizzes throughout, Accompanied by Jupyter notebooks that give sample calculations and methods to reproduce key results and graphs, An ideal textbook for advanced undergraduate and graduate students and an essential reference for researchers