Historically, the Foundational Principles articulated by Wright (1983) and others guided theory development, research and scholarship, and practice in rehabilitation psychology. In recent decades, these principles have become more implicit and less explicit or expressive in the writings and work of rehabilitation professionals. We believe that the Foundational Principles are essential lodestars for working with people with disabilities that can guide inquiry, practice, and service. To introduce this special issues, this commentary identifies and defines key Foundational Principles, including, for example, Lewin’s (1935) person–environment relation, adjustment to disability, the malleability of self-perceptions of bodily states, and the importance of promoting dignity for people with disabilities. We then consider the role the Foundational Principles play in the articles appearing in this special issue. We close by considering some new principles and their potential utility in rehabilitation settings. Readers in rehabilitation psychology and aligned areas (e.g., social–personality psychology, health psychology, rehabilitation therapist, psychiatry, and nursing) are encouraged to consider how the Foundational Principles underlie and can shape their research and practice.