A Modern Primer in Particle and Nuclear Physics provides a cohesive introduction to the fundamentals of the field and is designed to be accessible to undergraduate students. The textbook provides an ideal entry point and presents the modern concepts, theories, and experiments that explain the elementary constituents and basic forces of the universe. Starting with the basic concepts and definitions, the textbook goes on to cover core developments, such as the links between quantum chromodynamics and nuclear physics, the Higgs Boson, and the first observation of gravitational waves. New concepts are introduced gradually and clarified by intuitive explanations, exercises, and concrete examples linking particle physics to nuclear physics, astrophysics, and gravitation. The book also includes appendices on special relativity and non-relativistic quantum mechanics for those needing a basic grounding in these areas. The text is an expert guide for undergraduate physics students wanting to expand their knowledge, and also provides fascinating insights to graduate students, junior researchers, and physics enthusiasts.