An electrostatic discharge protection circuit includes a voltage drop circuit, a detector circuit, and a clamping circuit. The voltage drop circuit is configured to generate a second voltage according to a first voltage. The second voltage is smaller than the first voltage. The detector circuit is coupled to the voltage drop circuit. The detector circuit is configured to generate a control signal according to the second voltage and an input voltage. The clamping circuit is coupled to the voltage drop circuit and the detector circuit. The clamping circuit is configured to provide an electrostatic discharge path according to a voltage level of the control signal.