Fluoxetine, also known by the brand name Prozac, is a selective serotonin reuptake inhibitor (SSRI) commonly prescribed as an antidepressant. It works by increasing serotonin levels in the brain, which helps improve mood, emotions, and mental well-being. Fluoxetine is used to treat major depressive disorder, panic disorder, obsessive-compulsive disorder (OCD), bulimia nervosa, and other conditions.