While activism addressing AIDS in prisons cut across gender, people in women’s prisons played unique and important roles. This paper examines efforts to confront HIV/AIDS in prisons in the 1980s and 1990s United States, focusing on activism by women prisoners, women recently released, and the non-incarcerated activists who supported their work. I focus especially on collaborations between ACE (AIDS Counseling and Education, founded by people imprisoned in the Bedford Hills Correctional Facility for Women), ACE-OUT (a “sister program” for those recently released), and the Women’s Caucus of ACT UP. As they forged dialogue inside and across prison walls, they generated significant insights into the ties connecting prisons and AIDS: naming mass incarceration as a major factor accelerating the impact of AIDS on women, especially Black and Latinx women; identifying how the war on drugs subjected low-income women of color to two intersecting stigmas, criminalization and HIV; articulating women’s particular vulnerabilities to HIV brought into focus the epidemic’s intersections with racialized poverty and sexism. Perhaps most powerfully, they demonstrated how AIDS activism might challenge the growth and consequences of the carceral state at the moment of its most rapid expansion.