Atazanavir, trade name Reyataz®, (formerly known as BMS-232632) is an antiretroviral drug of the protease inhibitor (PI) class. Like other antiretrovirals, it is used to treat infection of human immunodeficiency virus (HIV).

Atazanavir is distinguished from other PIs in that it can be given once-daily (rather than requiring multiple doses per day) and has lesser effects on the patient's lipid profile (the amounts of cholesterol and other fatty substances in the blood). Like other protease inhibitors, it is used only in combination with other HIV medications.

The Food and Drug Administration (FDA) approved atazanavir on June 20, 2003. Atazanavir is the first PI approved for once-daily dosing, and also appears to be less likely to cause lipodystrophy and elevated cholesterol as side effects. It may also not be cross-resistant with other PIs. When boosted with ritonavir it is of equivalent potency to lopinavir for use in salvage therapy in patients with a degree of drug resistance.