Self-Determination Theory (SDT) is a broad theory of psychological growth and wellness that has revolutionized how we think about human motivation and the driving forces behind personality development. SDT focuses on people’s basic psychological needs for autonomy, competence, and relatedness and how social environments that support these needs foster more volition, vitality, and full functioning. SDT has supplied the basis for new and more effective practices in parenting, education, business, sport, healthcare, and other areas of life, fostering higher-quality motivation, engagement, and satisfaction. Drawing on over four decades of evidence-based research and application, The Oxford Handbook of Self-Determination Theory delivers a truly integrative volume by the top researchers and experts within the field of SDT. Edited by SDT co-founder Richard M. Ryan, this Handbook not only provides the theory’s historical and scientific underpinnings but also draws together the latest research and insights, covering topics from the social and biological underpinnings of motivation and wellness to practical applications in all aspects of life. This volume will be an invaluable resource for both researchers and practitioners, as well as any student of human nature, with practical research and guidance.