This conceptual article focuses on student engagement, and the use of digital games in language classrooms. In making a contribution to the mapping of student engagement across SLA (Dörnyei, 2019a), and in line with the need to use established theories to develop insights into engagement when L2 learning involves digital games, a case is made for the concept of immersion (Brown & Cairns, 2004). The concept is first introduced. Then, to explain how immersion can contribute in understanding student engagement with digital games, an example of engaged gameplay from a classroom ethnographic project in Sweden is provided. Drawing on this example, immersion is contrasted with the more established concepts of L2 willingness to communicate and flow. These comparisons show how immersion captures a form of engaged behaviour particular to playing video games, and which is distinct from other types of focused behaviour previously identified in L2 learning contexts. It is suggested that immersion can make a significant contribution to understanding engagement in contemporary classrooms: it captures engaged behaviour of varying intensity, validated measurement instruments exist, and it can be used in multi-variable designs. Although immersion captures engagement particular to gaming experiences, it has potential to extend to other digital technologies.