The α-Fe2O3 micro-ellipsoids were prepared using a facile hydrothermal process without any surfactant or template, and their morphological, structural and H2S sensing properties were investigated. The α-Fe2O3 showed uniform micro-ellipsoids with a long axis diameter of 1.7 μm and a short axis diameter of 1.2 μm. Detailed structural analysis confirmed that the synthesized α-Fe2O3 micro-ellipsoids were compact particles with a hexagonal structure. Gas sensor base on the α-Fe2O3 micro-ellipsoids showed excellent response, short response/recovery time (<90 s and 30 s, respectively), low detection concentration (~ 0.5 ppm), good long-term stability and excellent selectivity towards H2S gas at the optimized operating temperature of 350 °C. The sensing mechanism of the sensor based on the α-Fe2O3 micro-ellipsoids towards H2S was discussed.