Monitoring hazardous gases is increasingly critical for environmental protection and human health. As a novel class of two-dimensional nanomaterials, layered metal chalcogenides have attracted substantial research attention in recent years. This is attributed to their unique physical and chemical characteristics, which endow them with remarkable potential for applications in gas sensing. In particular, bismuth sulfide (Bi2S3) has been extensively studied recently due to its cost-effectiveness, abundance, and eco-friendliness, aligning with the requirements of advanced sensing platforms. This article systematically summarizes recent advancements in gas sensors based on Bi2S3. Initially, the structural and functional properties of Bi2S3 are outlined, emphasizing its potential in detecting toxic gases. Subsequently, innovative methodologies aimed at enhancing room-temperature sensing efficiency are critically analyzed. The discussion concludes by addressing existing limitations and proposing future research directions to optimize Bi2S3 for practical applications. This review aims to systematically examine the design and optimization of next-generation gas detection nanomaterials, offering fundamental understanding of their performance enhancement mechanisms and exploring their potential implementation across multiple technological platforms.