Mobile augmented reality is a subset of extended reality (XR), a broad category of technology tools and platforms reflecting a continuum from fully immersive virtual environments to augmented experiences that enrich place-based interactions. Unlike virtual reality, augmented reality (AR) does not construct a separate bounded reality and rather laminates digital information and elements onto the perceptible real-world environment. The focus here, mobile AR activities designed for second language use and learning, typically include participation in spatially arrayed story- or game-based narratives, tours of locations, or in-the-world quests that often involve physical movement through local and/or regional environments. This article describes the design of various AR interventions for language learning and reports empirical research findings in areas that include use of the target language, the learning outcomes of situated language use (vocabulary and construction learning), and observable patterns of collaboration in AR contexts. At its core, mobile AR ‘augments’ possibilities for human interaction and sense-making by laminating digital content onto the physically perceptible environment and holds transformative potential in both instructed and non-instructed language learning contexts.