The American Association on Intellectual and Developmental Disabilities (AAIDD) stands at the forefront of defining what constitutes intellectual disability. AAIDD promotes the vision that with appropriate supports, you can enhance a person with an intellectual disability’s ability to function in society of a person with intellectual disability. This course is part one of three parts on this topic, all of which are based on the book Intellectual Disability: Definition, Classification, and Systems of Support from AAIDD. The purpose of this course is to assist you in achieving a broad understanding of intellectual disability and its assessment. It covers the historical approaches to defining intellectual disability, as well as the current definition with its five essential assumptions. Also included in this course is an overview of the evolution of the construct’s boundaries, the multidimensional model of human functioning, the contextual basis of individualized supports, and the assessment framework and criteria. The ideal audience for this course includes psychologists, faculty, lawyers, physicians, service providers, special education teachers, and other disability professionals who seek information on defining, classifying, and diagnosing intellectual disability. Interactive exercises and case examples throughout the course will assist your learning so that you can apply these concepts when you need them most.