Hepatitis B virus (HBV) chronically infects over 300 million people worldwide. Many of them will die of chronic hepatitis or hepatocellular carcinoma. The present technology relates to the isolation and characterization of a novel neutralizing chimpanzee monoclonal antibody to HBV. The antibody was identified through a combinatorial antibody library constructed from bone marrow cells of a chimpanzee experimentally infected with HBV. The selected monoclonal antibody has been shown to react equally well with wild-type HBV and the most common neutralization escape mutant variants. Therefore, this monoclonal antibody with high affinity and broad reactivity may have distinct advantages over other approaches to immunoprophylaxis and immunotherapy of chronic HBV infection, as most of the monoclonal antibodies currently in use are not sufficiently and broadly reactive to prevent the emergence of neutralization escape mutants of HBV. This technology describes such antibodies, fragments of such antibodies retaining hepatitis B virus-binding ability, fully human or humanized antibodies retaining hepatitis B virus-binding ability, and pharmaceutical compositions including such antibodies. This invention further describes isolated nucleic acids encoding the antibodies and host cells transformed with nucleic acids. In addition, this invention provides methods of employing these antibodies and nucleic acids in the in vitro and in vivo diagnosis, prevention and therapy of HBV diseases.