Favipiravir (T-705) is a novel antiviral drug that selectively inhibits the RNA-dependent RNA polymerase (RdRP) of influenza and other RNA viruses. It is converted by cellular enzymes into its active form, favipiravir-ribofuranosyl-5'-triphosphate (RTP), which is recognized by the viral RNA polymerase as a purine nucleotide. Favipiravir is effective against a broad range of influenza viruses, including A(H1N1)pdm09, A(H5N1), and A(H7N9), and also inhibits influenza strains resistant to current antiviral drugs. It shows a synergistic effect when combined with oseltamivir, expanding treatment options for influenza. Clinical trials in Japan and the United States have demonstrated its safety and efficacy. Favipiravir also inhibits replication of many other RNA viruses, including arenaviruses, phleboviruses, hantaviruses, flaviviruses, enteroviruses, alphaviruses, paramyxoviruses, and noroviruses. Its unique mechanism of action and broad antiviral activity make it a promising candidate for treating influenza and other RNA viral diseases. Favipiravir is a prodrug that is phosphorylated in cells to RTP, which inhibits viral RNA polymerase. It may be misincorporated into viral RNA or act by binding to conserved polymerase domains, preventing nucleotide incorporation. Favipiravir has shown efficacy against arenaviruses, bunyaviruses, flaviviruses, alphaviruses, picornaviruses, and noroviruses. It is effective against severe viral infections, including those causing hemorrhagic fever and encephalitis. Clinical trials have shown that favipiravir is safe and effective, with a broad spectrum of antiviral activity. It is being evaluated for use in treating highly pathogenic bunyaviruses, including Rift Valley fever, Andes and Sin Nombre hantaviruses, and Crimean Congo hemorrhagic fever virus. Favipiravir's development as a novel therapy for influenza and other RNA viral diseases has potential to enhance national security and global public health.Favipiravir (T-705) is a novel antiviral drug that selectively inhibits the RNA-dependent RNA polymerase (RdRP) of influenza and other RNA viruses. It is converted by cellular enzymes into its active form, favipiravir-ribofuranosyl-5'-triphosphate (RTP), which is recognized by the viral RNA polymerase as a purine nucleotide. Favipiravir is effective against a broad range of influenza viruses, including A(H1N1)pdm09, A(H5N1), and A(H7N9), and also inhibits influenza strains resistant to current antiviral drugs. It shows a synergistic effect when combined with oseltamivir, expanding treatment options for influenza. Clinical trials in Japan and the United States have demonstrated its safety and efficacy. Favipiravir also inhibits replication of many other RNA viruses, including arenaviruses, phleboviruses, hantaviruses, flaviviruses, enteroviruses, alphaviruses, paramyxoviruses, and noroviruses. Its unique mechanism of action and broad antiviral activity make it a promising candidate for treating influenza and other RNA viral diseases. Favipiravir is a prodrug that is phosphorylated in cells to RTP, which inhibits viral RNA polymerase. It may be misincorporated into viral RNA or act by binding to conserved polymerase domains, preventing nucleotide incorporation. Favipiravir has shown efficacy against arenaviruses, bunyaviruses, flaviviruses, alphaviruses, picornaviruses, and noroviruses. It is effective against severe viral infections, including those causing hemorrhagic fever and encephalitis. Clinical trials have shown that favipiravir is safe and effective, with a broad spectrum of antiviral activity. It is being evaluated for use in treating highly pathogenic bunyaviruses, including Rift Valley fever, Andes and Sin Nombre hantaviruses, and Crimean Congo hemorrhagic fever virus. Favipiravir's development as a novel therapy for influenza and other RNA viral diseases has potential to enhance national security and global public health.