Reconfigurable radio frequency (RF) attenuators are critical passive components for 5G-Advanced and emerging 6G wireless systems. Conventional tunable attenuators rely on solid-state switches combined with fixed resistor networks, which suffer from unavoidable static power consumption and severe parasitic degradation at high frequencies. Here, we systematically demonstrate HfO₂-based non-volatile memristors as RF switches with tunable ON-state resistance (R_ON), enabling a switching-attenuation-integrated multistate attenuator. The fabricated Au/HfO₂/Ag devices exhibit stable bipolar resistive switching with an ON/OFF ratio exceeding 10⁹, reliable retention of 10⁵ s, and programmable R_ON continuously tuned from 5.8 Ω to 197.5 Ω. On-wafer RF characterizations from 10 MHz to 43.5 GHz reveal low insertion loss (−0.53 dB), high isolation (−26.8 dB), and clear scaling laws governing the effects of device geometry and R_ON on RF performance. Leveraging these unique characteristics, we propose a symmetric π-type programmable all-memristor attenuator architecture with a cascaded 2-unit configuration. The design achieves 12 discrete attenuation levels from 2 dB to 24 dB, a return loss better than 10 dB across the full band, and zero static power consumption without additional passive components or bias networks. This work establishes the fundamental material-device-RF performance relationship in HfO₂-based RF switches and provides a compact, low-power, and highly integrable solution for next-generation reconfigurable RF front-ends.