Sustainable development is relevant in all areas of education. Specific to language teaching, sustainability means fostering the competencies and skills that meet Education for Sustainable Development (ESD) objectives, which play a key role in achieving global Sustainable Development Goals (SDGs). The holism-pluralism-action-orientation framework, which forms the foundation of the transformation-oriented ESD approach, is based on pedagogical concepts and learning processes that support change agency and transformation. The pressure to integrate ESD into teaching is increasing worldwide. However, language education faces specific challenges because, unlike other subjects, language is both the medium and the content of teaching. In this introductory chapter, we define what transformative orientation means in language education and why it is necessary, and we discuss the significance of ESD in language teaching by reviewing previous studies on how language teachers implement it. We then discuss the possibilities and challenges associated with implementing transformation-oriented ESD in language education and language teacher education. The discussion centres on the concepts of activity, dialogue, and diversity allowing learners to express their views through discussions, thereby promoting ESD goals. Finally, we outline the structure of this volume and summarise the content of its chapters.