The TIMSS 2015 Encyclopedia: Education Policy and Curriculum in Mathematics and Science is a comprehensive compendium of how mathematics and science are taught around the world. Each TIMSS 2015 country and benchmarking participant prepared a chapter summarizing key aspects of mathematics and science education, and completed the TIMSS 2015 Curriculum Questionnaire. The chapters describe the structure of each education system, the mathematics and science curricula in the primary and lower secondary grades, and overall policies related to mathematics and science instruction. Taken together, the data from the curriculum questionnaire and the information in the chapters present a concise yet rich portrait of mathematics and science education globally, and make the TIMSS 2015 Encyclopedia an indispensable resource for policy and research in comparative education.