The number of older adults with dementia in U.S. prisons is rapidly rising. Yet, the vast majority of this marginalized subgroup of the aging population is left neglected behind bars without access to adequate medical and mental health care services. We assert that proactive, interdisciplinary collaborative efforts to improve practice, policy, and research and to develop a high-quality evidence-based continuum of care for this aging population are urgently needed. The overarching goals of this paper are to raise awareness of the life and experiences of persons with dementia in prison and to stimulate discussion, research, and advocacy efforts for this forgotten subgroup of older Americans. We describe the growing number of older adults with dementia in U.S. prisons, high-risk factors for dementia present in the prison population, and the life and experience of persons with dementia in the culture and environment of prison that is primarily not designed for them. We review the current state of services and programs for dementia in prison. We conclude by proposing practice, policy, and research-related priority areas and strategies for interdisciplinary gerontological responses.