An electrostatic discharge (ESD) protection circuit includes a clamp transistor, and inverter, a resistance-capacitance (RC) circuit, and a current mirror. The clamp transistor is coupled between a first supply node and a second supply node. The inverter has an input end and an output end, and the output end of the inverter is coupled with a gate of the clamp transistor. The RC circuit is coupled to the first supply node. The current mirror includes a first transistor and a second transistor. The first transistor is coupled between the input end of the inverter and the second supply node, and the second transistor is coupled between the RC circuit and the second supply node.