This book offers a critical exploration of definitions, methodologies and ideologies of English-medium instruction (EMI), contributing to new understandings of translanguaging as theory and pedagogy across diverse contexts. It brings together a number of conceptual and empirical studies on translanguaging in EMI at different educational levels, in a variety of countries, with different approaches to translanguaging, different named languages, and different policies. These studies include several underrepresented contexts across the globe, providing a broad view of how translanguaging in EMI is understood in these educational settings. Furthermore, this book addresses the complexities of translanguaging through a discussion of the affordances and constraints associated with the use of multiple linguistic resources in the EMI classroom.