Teacher Subject Identity in Professional Practice focuses on a key, but neglected, element of a teacher’s identity: that of their subject expertise. Studies of teachers’ professional practice have shown the importance of a teacher’s identity and the extent to which it can affect their resilience, commitment and ultimately their effectiveness. Drawing upon narrative research undertaken with a range of teachers over a period of 14 years, the book explores how subject expertise can play a significant role in teacher identity, acting as a professional compass guiding teachers at all levels of their professional practice. It reveals powerful individual stories of meaning-making which highlight the dynamic importance of teachers’ subject expertise The book’s metaphor of a professional compass goes to the heart of teacher professionalism, and provides a valuable mechanism to enable teachers to respond to challenges they face in their daily practice. It enables teachers to consider the moral dimensions of their practice, and can constitute a significant component in professional formation and identity. Throughout the book the importance of subject expertise for teachers’ professional practice is explored at a range of scales: from the classroom to broad education policy, and at different stages of a teacher’s career which offers readers a deeper understanding of the importance of subject expertise for teachers. Teacher Subject Identity in Professional Practice makes a significant contribution to an under-researched area. It identifies the role and significance of teachers’ subject expertise as a dimension of their teacher identity. The book is key reading for teacher educators, policy makers and researchers with an interest in teachers’ professional development and practice.