This book discusses the Universal Design for Learning (UDL) framework as essential tool for creating inclusive and effective mathematics classrooms and lessons in the twenty-first century. It emphasizes sustainable applications that directly address topics related to SDG 4 (Quality Education) and SDG 5 (Gender Equality). This book focuses on how UDL espouses the use of multiple means of representation, engagement and expression to accommodate the diverse learning needs of all students. It further highlights the need to integrate UDL principles in mathematics lessons, educators design instruction that is compelling, inclusive, accessible, engaging and challenging for every student, regardless of the characteristics (like abilities or backgrounds) that they bring into the classrooms. This book studies how the UDL principles can be used to design instruction that promotes critical thinking, problem-solving, collaboration, innovation and technological literacy, which are vital skills in the twenty-first century. It offers a holistic, research-driven and practical guide to UDL-based mathematics teaching, making it an invaluable resource for educators seeking impactful and inclusive strategies. What makes this book unique is its comprehensive approach to applying UDL, specifically in the context of mathematics education. The project outlines theoretical underpinnings and provides practical strategies and tools teachers can implement in their classrooms. The project offers research-based insights and real-world applications, thus making it a valuable knowledge resource for educators seeking to enhance their teaching practices.