This proceedings book contains papers presented at the International Symposium on Lightweight and Sustainable Polymeric Materials (LSPM23) held on February 17, 2023, and organized by King Mongkut’s University of Technology North Bangkok, Thailand. The papers in this book are presented by academics and industrial practitioners showcasing the latest technological advancements and applications of environmentally friendly polymeric materials with the emphasis on the production of lightweight, low-cost, low-energy-consuming materials with competitive performance. The content of this book appeals to academia and industrial researchers from the fields of polymer chemistry, physics, and materials science.