This book explores current research on online instructed L2 acquisition, with a specific focus on the nature and impact of learner engagement in online L2 classroom interaction. It examines the topic of online learner engagement from various theoretical perspectives, discusses conceptual and methodological issues, synthesizes research on the role of learner engagement in online L2 classroom interaction, and critically assesses its connection to teaching practices across different L2 settings. The book is intended for a wide audience, including undergraduate and postgraduate Applied Linguistics, TESOL and Second Language Education students seeking to understand the significance of learner engagement in online L2 learning. It will also be useful for researchers interested in staying updated on recent findings regarding the benefits of learner engagement in online classroom interaction for L2 learning. Additionally, teachers, teacher trainers and educators in Teacher Education (TE) and/or continuous professional development (CPD) programs can benefit from the pedagogical insights offered in this book regarding online L2 instruction in various contexts.