This edited volume aims to advance a transperspectival approach (Tao & Gao, 2021) in exploring and understanding language teacher agency (Hawkins & Mori, 2018). It presents studies that illustrate methodological innovations for researching language teacher agency such as longitudinal studies and new data collection methods such as multimodal narratives and social network analysis. The studies not only delve into language teachers' diverse advocacy actions globally but also provide actionable practices for readers to understand and implement agency in their own contexts. The book brings together contributions from scholars based in diverse global contexts, including Hong Kong, Australia, the Philippines, the United States, the Netherlands, Kazakhstan, Egypt, the United Kingdom, Japan, and Ukraine, reflecting the rich geographical and cultural diversity of language teacher agency research. Encompassing EFL, ESL, and multilingual education settings, the book illuminates the myriad ways teachers demonstrate agency in both formal and informal learning environments while advocating for their students, profession, colleagues, institutions, and themselves. Additionally, the edited volume is intended to equip the teachers of multilingual learners of English with the skills to advocate for themselves effectively. Through practical examples and strategies, this volume aims to empower educators and learners alike to navigate complex educational landscapes, advocating for change and using agency to effect positive outcomes.