Introduction to Sociological Theory: Theorists, Concepts, and Their Applicability to the Twenty-First Century introduces students to the major traditions of sociological thought by integrating classical and contemporary theories into a single, coherent framework. The book explains the ideas of influential thinkers such as Karl Marx, Émile Durkheim, Max Weber, Talcott Parsons, Robert Merton, Michel Foucault, Pierre Bourdieu, and leading feminist, interactionist, conflict, globalization, and race theorists. The text combines excerpts from original theoretical writings with detailed explanations, historical context, timelines, biographies, and practical examples drawn from societies around the world. It demonstrates how sociological theories can be applied to understand contemporary issues including globalization, inequality, power, culture, gender, race, technology, identity, and social change. Designed primarily for undergraduate and postgraduate sociology students, the book develops critical thinking by connecting foundational theories with present-day social problems and research. It serves as both an introductory textbook and a reference for understanding the evolution and continuing relevance of sociological theory.