We theorize 5 dimensions of academic disengagement based on students' values, motivations, study behaviors, academic interactions, and competing involvements. Using 2010 survey data from the University of California, we find support for this conceptualization. The size of disengaged populations varied between 5% and 25%, depending on the measure used. On most measures, male students, upper-division students, students with low college GPAs, and students in the humanities and social sciences were significantly more likely, net of covariates, to be among academically disengaged populations. Students with high SAT scores were also more likely to be among academically disengaged populations.