Intriguing physical and chemical properties of atomically thin semiconductors provide avenues for the development of the next-generation electronics, optoelectronics, and sensing applications. However, many materials are intrinsically nonlayered and therefore difficult to obtain in two dimensions (2D) due to the presence of strong in-plane bonds. Here, we adopted liquid metal synthetic strategies to produce 2D gallium sulfide (Ga2S3), which is an intrinsically nonlayered material. The obtained monoclinic α-Ga2S3 has a relatively high field-effect mobility of 3.5 cm2 V–1 s–1 and features a p-type material with a bandgap of 2.1 eV. Photodetectors that are made based on these synthesized 2D Ga2S3 exhibit relatively strong photodetectivity of 1010 jones and photoresponsivity of 240 A W–1 in visible wavelengths. The 2D Ga2S3 is also found to be suitable for sensing of nitrogen dioxide (NO2) gas at low evaluated temperatures. Excellent electronic, optical, and gas sensing performance demonstrated in this work offers great promises for synthesizing high quality 2D materials based on the liquid metal framework.