The Elements of Polymer Science and Engineering, Third Edition, is a textbook for one- or two-semester introductory courses in polymer science and engineering taught primarily to senior undergraduate and first-year graduate students in a variety of disciplines, but primarily chemical engineering and materials science. Since the publication of the second edition in 1999, the field of polymers has advanced considerably. A key feature of this new edition is the inclusion of new concepts such as polymer nanocomposites and metallocene catalysts in existing chapters as well as new chapters covering selected contemporary topics such as behavior of natural polymers, polymer dynamics, and diffusion in polymers. This book has been completely reorganized to become more aligned with how instructors currently teach the course. There are now several enhancements to the book's pedagogy, including the addition of numerous worked examples and new figures to better illustrate key concepts and the addition of a large number of end-of-chapter exercises, many of which are based on recently published research and relevant industrial data. This third edition will appeal to advanced undergraduate and graduate students in the physics, chemistry, and chemical engineering departments who are taking courses related to polymer science and engineering, as well as engineers new to the field of polymers.