An electrostatic discharge (ESD) protection apparatus includes a clamp circuit, a detection circuit and a control circuit. The clamp circuit has a first terminal and a second terminal respectively coupled to a first rail line and a second rail line. In response to an ESD event, the clamp circuit generates a first coupling potential at its coupling terminal. The detection circuit, coupled to the coupling terminal of the clamp circuit and the second rail line, outputs a detection signal in response to the first coupling potential. The control circuit, coupled to the first and second rail lines, the detection circuit and the clamp circuit, outputs a conduction signal to a control terminal of the clamp circuit in response to the detection signal. The clamp circuit is conducted in response to the conduction signal so that ESD between the first and second rail lines is performed through the clamp circuit.