Abstract: The object of the invention are monoclonal antibodies against hemagglutinin of H5-serotype influenza viruses selected from the group comprising G-1-31-22, G-2-14-10, G-5-32-5, G-6-42-42, G-7-24-17 and G-7-27-18, having a broad application in immunoprophylaxis and immunotherapy of infections evoked by H5-serotype influenza viruses in humans and animals. The invention also provides hybridomas producing said antibodies, as well as compositions and diagnostic kits containing said antibodies for the detection and typing of H5-serotype influenza viruses and antibodies against H5-serotype influenza viruses in biological samples.