The term inclusion began appearing in the literature on special education in the late 1980s. The term represented an evolutionary step in the field’s efforts to develop models of education that would allow students with intellectual and developmental disorders to be educated with their peers without disabilities. Unlike the previous movements of “mainstreaming” and “integration,” which focused on the simple physical placement of students in typical schools and classrooms, the inclusion movement focused on promoting students’ full participation in the academic and social activities of typical schools and classrooms. This entry discusses the characteristics of inclusion, the number of students served in inclusive settings, how inclusion affects educational and social outcomes, and potential directions for research and teacher collaboration involving inclusion.