Gas sensors play an essential role in modern life, with applications including leakage detection, environmental monitoring, industrial safety, and healthcare. As the demand for portable, autonomous, and low-maintenance sensing systems grows, self-powered gas sensors are gaining attention. Self-powered gas sensors represent a new frontier in sensing technology, offering autonomous operation by harvesting energy from ambient sources such as mechanical motion, light, heat, or chemical gradients. This chapter explores the fundamental principles underlying self-powered gas sensors, including the integration of energy harvesting mechanisms such as piezoelectric, triboelectric, thermoelectric, and photovoltaic systems with various gas sensing technologies. This chapter also highlights challenges and future direction for self-powered gas sensors.