This study presents a method for the epitaxial growth of large-scale, single-crystal monolayer molybdenum disulfide (MoS₂) on c-plane sapphire substrates through precise control of the S/MoO₃ precursor ratio. The research demonstrates the successful growth of 2-inch single-crystal MoS₂ monolayers with high uniformity and quality, characterized by excellent phonon circular dichroism, exciton valley polarization, high room-temperature mobility, and a high on/off ratio. The method enables the seamless alignment and stitching of MoS₂ domains across the entire wafer, achieving a high-quality, single-crystal monolayer with no grain boundaries. The epitaxial MoS₂ monolayers exhibit state-of-the-art performance, including a room-temperature mobility of ~140 cm²/V·s and an on/off ratio of ~10⁹. The study provides a simple and effective strategy for the large-scale synthesis of high-quality 2D semiconductors on commercial substrates, paving the way for the development of 2D electronic circuits and further extending Moore's law. The results demonstrate the potential of MoS₂ as a promising candidate for next-generation electronic devices.This study presents a method for the epitaxial growth of large-scale, single-crystal monolayer molybdenum disulfide (MoS₂) on c-plane sapphire substrates through precise control of the S/MoO₃ precursor ratio. The research demonstrates the successful growth of 2-inch single-crystal MoS₂ monolayers with high uniformity and quality, characterized by excellent phonon circular dichroism, exciton valley polarization, high room-temperature mobility, and a high on/off ratio. The method enables the seamless alignment and stitching of MoS₂ domains across the entire wafer, achieving a high-quality, single-crystal monolayer with no grain boundaries. The epitaxial MoS₂ monolayers exhibit state-of-the-art performance, including a room-temperature mobility of ~140 cm²/V·s and an on/off ratio of ~10⁹. The study provides a simple and effective strategy for the large-scale synthesis of high-quality 2D semiconductors on commercial substrates, paving the way for the development of 2D electronic circuits and further extending Moore's law. The results demonstrate the potential of MoS₂ as a promising candidate for next-generation electronic devices.