Ultrafast response/recovery and high selectivity of gas sensors are critical for real-time and online monitoring of hazardous gases. In this work, α-Fe2O3 nano-ellipsoids were synthesized using a facile one-step hydrothermal method and investigated as highly sensitive H2S sensing materials. The nano-ellipsoids have an average long axis diameter of 275 nm and an average short axis diameter of 125 nm. H2S gas sensors fabricated using the α-Fe2O3 nano-ellipsoids showed excellent H2S sensing performance at an optimum working temperature of 260 ℃. The response and recovery times were 0.8 s/2.2 s for H2S gas with a concentration of 50 ppm, which are much faster than those of H2S gas sensors reported in literature. The α-Fe2O3 nano-ellipsoid based sensors also showed a high selectivity to H2S compared to other commonly investigated gases including NH3, CO, NO2, H2, CH2Cl2 and ethanol. In addition, the sensors exhibited high response values to different concentrations of H2S with a detection limit as low as 100 ppb, as well as excellent repeatability and long-term stability.