In 2019, the viral pandemic known as COVID-19 touched and indelibly impacted the global community, including the United States. The impact of COVID-19 was particularly onerous for the US’s incarcerated. Not only is the United States the leading incarcerator in the world, but the the carceral system represents the nation’s largest de facto mental health treatment setting. The carceral system is overrepresented by people of color, people with disabilities, and people of lower socioeconomic status—with great overlap between these populations. In combination with tough-on-crime policies, the US prison population also now finds itself aging, a process accelerated by confinement. The present systematic literature review describes the current state of peer-reviewed scholarship addressing the impact of COVID-19 on mental illness, incarceration, and their intersection in the United States. To be considered for inclusion, articles (1) were based in the United States or, if a global study, explicitly inclusive of the United States; (2) addressed COVID-19 and mental illness, COVID-19 and US incarceration, or COVID-19 and mental illness and US incarceration; and (3) were published or in-press between December 2019 and October 2021, as either a peer-reviewed commentary or research article in an academic journal. The final literature sample yielded 34 peer-reviewed articles. Ten themes and accompanying figures were developed within each of the three intersections: Intersection #1, COVID-19 and mental illness; Intersection #2, COVID-19 and US incarceration; and Intersection #3, COVID-19 and mental illness and US incarceration. Implications for respective US policies, programs, and systems are discussed.