This study reports the identification and characterization of a human monoclonal antibody (mAb) named 47D11, which neutralizes both SARS-CoV and SARS-CoV-2 in cell culture. The antibody targets a conserved epitope on the spike receptor-binding domain (RBD) of these viruses, allowing it to cross-neutralize both SARS-CoV and SARS-CoV-2. The 47D11 mAb was generated from a collection of hybridomas derived from immunized transgenic H2L2 mice and reformatting into a fully human immunoglobulin. The antibody was found to inhibit infection of VeroE6 cells pseudotyped with SARS-CoV and SARS-CoV-2 spike proteins, as well as authentic SARS-CoV and SARS-CoV-2 infections. The binding properties of 47D11 were characterized using ELISA, flow cytometry, and biolayer interferometry, revealing its ability to bind the RBD without interfering with receptor interaction. The study suggests that 47D11 may offer potential for the prevention and treatment of COVID-19 and other emerging diseases caused by viruses from the Sarbecovirus subgenus.This study reports the identification and characterization of a human monoclonal antibody (mAb) named 47D11, which neutralizes both SARS-CoV and SARS-CoV-2 in cell culture. The antibody targets a conserved epitope on the spike receptor-binding domain (RBD) of these viruses, allowing it to cross-neutralize both SARS-CoV and SARS-CoV-2. The 47D11 mAb was generated from a collection of hybridomas derived from immunized transgenic H2L2 mice and reformatting into a fully human immunoglobulin. The antibody was found to inhibit infection of VeroE6 cells pseudotyped with SARS-CoV and SARS-CoV-2 spike proteins, as well as authentic SARS-CoV and SARS-CoV-2 infections. The binding properties of 47D11 were characterized using ELISA, flow cytometry, and biolayer interferometry, revealing its ability to bind the RBD without interfering with receptor interaction. The study suggests that 47D11 may offer potential for the prevention and treatment of COVID-19 and other emerging diseases caused by viruses from the Sarbecovirus subgenus.