Self-determination theory is a generalized theory of behavior that focuses on motivation quality and psychological need satisfaction as preeminent behavioral determinants. The theory distinguishes between autonomous and controlled forms of motivation. Autonomous motivation reflects willingly engaging in behaviors for self-endorsed reasons, whereas controlled motivation reflects engaging in behavior for externally or internally pressured or controlled reasons. Satisfaction of the needs for autonomy, competence, and relatedness is necessary for optimal functioning and well-being, and influences the form of motivation, autonomous or controlled, experienced by individuals when acting. Autonomous motivation is consistently related to sustained behavior change and adaptive outcomes. Interventions to promote autonomous motivation have targeted psychological need support provided by social agents (e.g., leaders, managers, teachers, health professionals), particularly autonomy need support. Interventions using need-supportive techniques have demonstrated efficacy in promoting autonomous motivation, behavior change, and adaptive outcomes. Research has identified behaviors displayed, and language used, by social agents, or communicated by other means, that support autonomous motivation. Autonomy-support training programs have been developed to train social agents to promote autonomous motivation and behavior change. Future research needs to examine the unique and interactive effects of specific autonomy-support techniques, provide further evidence for long-term efficacy, and examine “dose” effects and long-term efficacy.