The fundamental Boltzmann limitation dictates the ultimate limit of subthreshold swing (SS) to be 60 mV dec^-1 , which prevents the continued scaling of supply voltage. With atomically thin body, 2D semiconductors provide new possibilities for advanced low-power electronics. Herein, ultra-steep-slope MoS₂ resistive-gate field-effect transistors (RG-FETs) by integrating atomic-scale-resistive filamentary with conventional MoS₂ transistors, demonstrating an ultra-low SS below 1 mV dec^-1 at room temperature are reported. The abrupt resistance transition of the nanoscale-resistive filamentary ensures dramatic change in gate potential, and switches the device on and off, leading to ultra-steep SS. Simultaneously, RG-FETs demonstrate a high on/off ratio of 2.76 × 10⁷ with superior reproducibility and reliability. With the ultra-steep SS, the RG-FETs can be readily employed to construct logic inverter with an ultra-high gain ≈2000, indicating exciting potential for future low-power electronics and monolithic integration.