Transformative L2 Teacher Education Innovations features empirical research studies informed by Vygotskian Sociocultural Theory (VSCT) that are explicitly and intentionally designed to transform second language (L2) teacher reasoning and thinking, as well as L2 teaching practices and pedagogical choices. With contributions from scholars and practicing teacher educators, each chapter highlights a designed innovative professional development experience that has created a “new” social situation of development with a clearly articulated “ideal” for L2 teachers to embrace and/or achieve.Each study articulates the rationale and unique design features of the innovation, the intentionality behind the choices made when designing and enacting the innovation, and the quality, character, and outcomes of the intervention for L2 teachers.Furthermore, each study documents the forms of mediation that are offered to support L2 teacher professional development, such as conceptual tools, goal-directed activities, and/or social relations/interactions. The book offers insight into the internal logic of VSCT-informed L2 Teacher Education and provides concrete examples of how L2 teacher educators can adopt a Vygotskian-informed pedagogical stance in their teacher education practices.The edited collection is especially applicable for scholars and teacher educators in language education, applied linguistics, TESOL, and bilingual education who engage with Vygotskian Sociocultural Theory.