Atazanavir is a chemical with the molecular formula C38H52N6O7. The density is 1.178g/cm3; it is a crystalline solid.

Atazanavir, sold under the trade name Reyataz, is an antiretroviral drug of the protease inhibitor (PI) class. Like other antiretroviruses, it is used to treat human immunodeficiency virus (HIV) infection.

Atazanavir differs from other PIs in that it can be given once a day (rather than requiring multiple doses per day) and has less effect on a patient's lipid profile (the amount of cholesterol and other fatty substances in the blood). Like other protease inhibitors, it is only used in combination with other HIV drugs.

Atazanavir was approved by the U.S. Food and Drug Administration (FDA) on June 20, 2003. Atazanavir is the first PI approved for once-daily dosing and appears unlikely to cause lipodystrophy and elevated cholesterol as side effects. It may also not be cross-resistant with other PIs. When boosted with ritonavir, its efficacy as lopinavir is equivalent to rescue therapy for patients with some degree of resistance, although ritonavir boosting reduces atazanavir metabolism Advantage.

It is on the World Health Organization's list of essential medicines and is the most important medicine needed for an essential health system.