Diflucan, the brand name for fluconazole, is an antifungal medication used to treat and prevent various fungal infections. It is effective against infections caused by fungi that can affect different parts of the body, including the mouth, throat, esophagus, lungs, bladder, genital area, and bloodstream. Diflucan is also used to prevent fungal infections in individuals with weakened immune systems, such as those undergoing cancer treatment or living with HIV/AIDS.