This chapter focuses on the notion of teacher leadership. Although this topic is of major significance, as it portrays teachers as facilitators of school reform and improvement, it has not been given much attention in the field of English language teaching. Contemporary English language education needs teachers who can passionately implement effective and innovative practices in the classroom, develop and take ownership of new pedagogical strategies, utilise professional knowledge to contribute to school improvement plans, and establish close relationships with other school stakeholders to enhance the student learning experience as well as overall school functioning. With this in mind, this chapter defines the concept of teacher leadership and presents a profile of a teacher leader who can exert their influence, both in the classroom and in the wider school, through a variety of formal and informal channels. This is followed by a discussion of the process of developing teacher leadership. Among other things, this touches upon different types of leadership and power and provides strategies to support teachers in their development as leaders. Next, the principles of successful teacher leadership are presented. A brief discussion of leadership through mentoring teachers concludes the chapter.