The world is home to an extraordinary level of linguistic diversity, with roughly 7,000 languages currently spoken and signed. Yet this diversity is highly unstable and is being rapidly eroded through a series of complex and interrelated processes that result in or lead to language loss. The combination of monolingualism and networks of global trade languages that are increasingly technologized have led to over half of the world’s population speaking one of only 13 languages. Such linguistic homogenization leaves in its wake a linguistic landscape that is increasingly endangered. A wide range of factors contribute to language loss and attrition. While some—such as natural disasters—are unique to particular language communities and specific geographical regions, many have similar origins and are common across endangered language communities around the globe. The harmful legacy of colonization and the enduring impact of disenfranchising policies relating to Indigenous and minority languages are at the heart of language attrition from New Zealand to Hawai’i, and from Canada to Nepal. Language loss does not occur in isolation, nor is it inevitable or in any way “natural.” The process also has wide-ranging social and economic repercussions for the language communities in question. Language is so heavily intertwined with cultural knowledge and political identity that speech forms often serve as meaningful indicators of a community’s vitality and social well-being. More than ever before, there are vigorous and collaborative efforts underway to reverse the trend of language loss and to reclaim and revitalize endangered languages. Such approaches vary significantly, from making use of digital technologies in order to engage individual and younger learners to community-oriented language nests and immersion programs. Drawing on diverse techniques and communities, the question of measuring the success of language revitalization programs has driven research forward in the areas of statistical assessments of linguistic diversity, endangerment, and vulnerability. Current efforts are re-evaluating the established triad of documentation-conservation-revitalization in favor of more unified, holistic, and community-led approaches.