This article examines the growing significance of multilingualism in contemporary English Language Teaching (ELT) and the pedagogical shifts it has prompted. Traditionally, ELT was shaped by monolingual ideologies that treated learners' first languages as obstacles to acquiring English and encouraged the exclusive use of the target language in classrooms. Drawing on recent scholarship in applied linguistics and sociolinguistics, this article argues that these assumptions have been substantially revised: multilingual learners' existing linguistic resources are now understood as assets rather than as interference. The discussion traces the conceptual shift from monolingual to multilingual perspectives, with particular attention to translanguaging as an emerging pedagogical paradigm that treats language use as an integrated, flexible repertoire rather than as separate systems. It further considers the cognitive benefits associated with multilingualism, including metalinguistic awareness, cognitive flexibility, and intercultural competence, before situating these debates within the linguistically diverse context of Indian classrooms. The article concludes by outlining implications for curriculum design, classroom pedagogy, assessment, and teacher education, arguing that ELT must move beyond monolingual norms to reflect the multilingual realities of twenty-first-century learners.