Abstract The realization of thermally robust, polymer‐based radio‐frequency (RF) switches for flexible millimeter‐wave (mmWave) electronics is a long‐standing challenge due to inherent material instability. Here, a novel high‐performance, thermally stable polymer‐based non‐volatile analogue switch is reported, utilizing an Au/poly(1,3,5‐trimethyl‐1,3,5‐trivinyl cyclotrisiloxane) (pV3D3)/Au memristive structure. A gold filamentary conduction model is elucidated that governs the device's resistive switching, enabling analogue switching operations. Fabricated via a wafer‐scale compatible initiated chemical vapor deposition technique, the device overcomes the limitations of prior organic electronics, exhibiting notable high‐temperature stability with a projected state retention of over 10 years at 128.7 °C and robust endurance exceeding 1600 cycles. Furthermore, the switch demonstrates excellent RF performance suitable for mmWave applications, featuring a cutoff frequency of 5.38 THz, low insertion loss (<0.4 dB), high isolation (>18 dB) up to 20 GHz, and stable operation up to 67 GHz. Successful implementation on a flexible substrate confirms its mechanical resilience for wearable systems. This work establishes a viable pathway for robust, polymer‐based analogue switches in advanced flexible RF technologies.