A one-step reverse transcription loop-mediated isothermal amplification (RT-LAMP) was developed for the rapid and sensitive detection of human norovirus (HuNoV) in oysters. HuNoV, a leading cause of foodborne gastroenteritis, is frequently associated with contaminated oysters, necessitating a reliable on-site detection method. RT-LAMP was designed using primers targeting conserved regions of HuNoV genogroups I (GI) and II (GII). This method demonstrated a detection limit of 101 genome copies per microliter, surpassing the sensitivity of semi-nested RT-PCR and real-time RT-PCR. The restriction fragment length polymorphism analysis confirmed specificity, ensuring no cross-reactivity with other foodborne pathogens. RT-LAMP reaction was optimized for isothermal amplification at 63 °C, completed within 60 min. Viral RNA was extracted using the QIAamp Viral RNA Mini Kit, and results were visualized through agarose gel electrophoresis or colorimetric detection with SYBR Green I dye. Field tests using artificially contaminated oyster samples confirmed the reliability and accuracy of RT-LAMP, making it suitable for on-site applications in the oyster industry. This study highlights the potential of one-step RT-LAMP as a practical, rapid, and sensitive diagnostic tool for HuNoV detection. Its simplicity, cost-effectiveness, and ability to deliver results without sophisticated equipment make it an ideal solution for enhancing food safety and preventing HuNoV outbreaks. Such advancements are anticipated to strengthen the global competitiveness of the oyster industry by ensuring the microbiological safety of seafood products.