This book addresses the critical gaps among understandings of teacher leadership across organizational and cultural contexts. It challenges the use of the term teacher leadership as if there is a widely shared understanding of what it is and what it means for exercising influence and making decisions. The book describes how implicit meanings and competing assumptions about teacher leadership may contribute to uncertainty and confusion in school communities. The authors caution against the incorporation of teacher leadership in international policy making discussions without adequate consideration of contextual, organizational, historical, and cultural differences that may lead to school community members struggling to accommodate the concept or, worse, ignoring other frameworks for facilitating more culturally appropriate decision making. This book shares the findings of research conducted in several North American, European, African, Latin-American, and Australasian contexts as part of the International Study of Teacher Leadership. Study findings are used to posit contextualized conceptualizations of teacher leadership and to offer a perspective for positioning researchers and practitioners in the international teacher leadership discourse.