An electrostatic discharge protection circuit is provided. First NMOS transistor is coupled to a power line. Second NMOS transistor is coupled between the first NMOS transistor and a ground. Detection unit provides a detection signal when an ESD event occurs at the power line. Trigger unit turns on the second NMOS transistor and the first NMOS transistor in sequence in response to the detection signal. Discharge path is formed from the power line to the ground via the first and second NMOS transistors. First PMOS transistor is coupled between the power line and a gate of the second NMOS transistor. Third NMOS transistor is coupled between the ground and the gate of the second NMOS transistor. Second PMOS transistor is coupled between the gates of the first and second NMOS transistors. Third PMOS transistor is coupled between the power line and the first PMOS transistor.