The present disclosure describes aspects of Zener overvoltage protection (OVP) with a thermal trigger for an implant. In some aspects, an apparatus comprises a rectifier disposed in a rectification circuit and configured to rectify alternating current (AC) power received at the rectification circuit to direct current (DC) power. The apparatus also includes a Zener diode and thermistor. The Zener diode is disposed in the rectification circuit between the rectifier and an output terminal, and is configured to clamp the DC power at a predefined voltage. The clamped DC power output at the output terminal is usable by the implant. The thermistor and Zener diode are disposed in temperature-measuring proximity. This enables the thermistor to measure a temperature of the Zener diode, which correlates to voltage at the Zener diode due to clamping. When the measured temperature exceeds a threshold temperature indicative of an OVP condition, remedial OVP actions are initiated.