AbstractThe usage of the gas sensor has been increasing very rapidly in the industry and in daily life for various potential applications. In the recent years, metal oxide semiconductors (MOS) become the primary choice for designing highly sensitive, stable, and low‐cost real‐life applications‐based gas sensors due to their inherent physical and chemical properties. Researchers have proposed numerous sensing mechanisms to explain the functionality of MOS‐based gas sensors. In this review, we have comprehensively covered different sensing mechanisms used for MOS. We have also discussed different parameters affecting the sensitivity and selectivity of the gas sensors. Moreover, the different techniques used to enhance the gas sensing response of MOS‐based sensors are also extensively covered. And finally, we give our prospective on recent opportunities and challenges on the future applications of MOS‐based gas sensors.