This chapter defines the concept of leadership and describes the most common leadership theories. Most scholars agree that leadership is a key component of organizational effectiveness. The very range of definitions of leadership and the absence of consensual agreement between the definitions make the concept of leadership an issue in itself. The chapter examines leadership from various perspectives with an emphasis on the influence of particular leadership styles on the financial sustainability of a nonprofit organization. It integrates theory-based and practice-based approaches, and thus provides tools to better understand and influence the leader-follower dynamic in the nonprofit setting. Early leadership theories include: Great man theory, traits theories, behavioral theories, contingency theories, and attribution and charismatic theories. The chapter explains the relationship between leadership and community relations and discusses the role of leadership in strategic planning. It also explains the relationship between leadership and financial sustainability of nonprofit organizations.