This book is a revised, extended, and updated version of our successful textbook Introductory Quantum Physics and Relativity. It is based on lectures that were originally given as part of the undergraduate degree programme at the University of Leeds, but has been extended and modified to bring it up to date with recent developments. The book contains all the material required for quantum physics and relativity in the first two years of a typical physics degree, but also contains more interesting and up-to-date extensions and applications such as quantum field theory, entanglement, and quantum information science.