In response to widespread interest in 21st-century learning across the educational landscape, the authors explored the extent to which the concept possesses clear definition and coherent meaning within both research discourse and K-12 classroom practice in the United States, particularly with regard to conceptualizations and enactments of literacy. This research review offers descriptive data about the subject areas and grade levels in which 21st-century learning efforts are concentrated, analyzes the literacy frameworks employed to guide pedagogy, and describes instructional practices most frequently associated with the concept. Further, this research review explores the role of digital tools in the enactment of 21st-century learning, including how often teachers are leveraging the collaborative and interactive affordances of those tools. By leveraging a critical analytic framework, findings indicate a dearth of classroom-based research emphasizing democratic engagement and equity within 21st-century learning, as well as a hesitancy to use digital literacies to connect with wider publics. Analysis suggests a weakly defined understanding of what literacy learning in the 21st century means in classrooms today, which speaks to the need for a stronger focus on social futures.