This entry traces the evolution of strength-based leadership within the broader context of positive psychology, identifying three distinct developmental phases. Initially focused on identifying and amplifying positive traits and states, strength-based leadership matured through recognition of the risks of overuse, limited context sensitivity, and excessive individualism. The second wave introduced balance by integrating negative emotions, meaning, and context, while the third wave foregrounds situational, ethical, and planetary concerns. Strengths are now increasingly assessed and developed not only for individual efficacy but also for team, organizational, and systemic impact. The entry reviews the psychometric and methodological implications of strengths assessment, the nuanced relationship between strengths and leadership outcomes, and the shifting purpose of strengths use towards self-transcendence and sustainability. Limitations and research gaps are identified, particularly around context-sensitivity, measurement validity, and the need for systemic outcome indicators.