Tenofovir is an antiviral medication primarily used to treat human immunodeficiency virus (HIV) and hepatitis B virus (HBV) infections. It belongs to a class of drugs known as nucleotide reverse transcriptase inhibitors (NRTIs), which work by blocking the reverse transcriptase enzyme, preventing the virus from replicating in the body. In addition to its use in treating HIV and HBV, tenofovir is also a key component in pre-exposure prophylaxis (PrEP) for individuals at high risk of contracting HIV. This preventive approach significantly reduces the chances of infection when taken consistently, making it an important tool in public health efforts against the spread of HIV.