This paper develops a framework for exploring resonances across human and nonhuman carceral geographies. I illustrate the close linkages across prisoner and animal carcerality and captivity focusing on three types of sites and institutions: the prison execution chamber and the animal slaughterhouse; sites of laboratory testing of pharmaceutical and other products on incarcerated humans and captive animals; and sites and institutions of exploited prisoner and animal labor. The main themes that call for a “carceral comparison” among these sites include: the emotional and psychological strain and violence enacted on bodies that is interwoven into their day‐to‐day operations; their geographies (locations, design, and layout) and carefully regulated movements within them; relationships between carcerality and “purpose breeding” that extends across both nonhuman and human populations; the ways in which “animalization” of incarcerated bodies works to create conditions for social death and killability; and the legal and political contexts that produce certain lives as disposable “bare lives”.