An accessible but rigorous treatment of the theoretical foundations of population genetics. Population genetics—the branch of evolutionary biology concerned with understanding how and why populations’ genetic compositions change over time—rests on a well-developed theoretical foundation that draws on genetics, mathematics, and computer science. This textbook provides an approachable but rigorous treatment for advanced undergraduate and graduate students interested in building a quantitative understanding of the genetics of evolution. Existing texts either assume very mathematically advanced readers, or avoid much of the underlying theory, instead focusing on current methods of data analysis. In contrast, The Foundations of Population Genetics develops the theory from first principles. Requiring only confidence in algebra, this self-contained, student-friendly book illustrates the conceptual framework, terminology, and methods of mathematical modeling. It progressively introduces concepts from genetics as needed, while emphasizing biological implications throughout. As a result, readers come away with a deep understanding of the structure of population genetics without needing to master its mathematics. Connects theory with the most recent genetic data better than existing texts Features engaging real-world examples and extensive original figures Provides dozens of carefully scaffolded questions that deepen the reader's understanding of key concepts Ideal as a succinct reference for established scientists in biology, medicine, and computer science Instructor resources available