In this second edition of the classic work Foundations of Mathematical Genetics, a definitive account is given of the basic models of population genetics together with the historical origins of its development since 1908. This book satisfies the need for a more careful study of the foundations of mathematical population genetics, treating the simple deterministic models for random-mating diploid populations in depth without sacrificing clarity of expression. In the second edition, coverage has been extended with the provision of a new chapter on the Fundamental Theorem of Natural Selection. This book is written for those interested in the mathematical aspects of genetics, ecology, and biology. Students and historians of mathematical genetics will find this work a definitive statement of the origins of modern mathematical population genetics.