An electrostatic discharge protection circuit protects the internal circuits of a semiconductor. The electrostatic discharge protection circuit includes a first electrostatic protection unit connected to a power source supply pad. The first electrostatic protection unit discharges an ESD current into the power source supply pad when an ESD is introduced into the input/output pad, and generates a first driving voltage by utilizing the ESD current flow through a voltage-drop unit. A driver driven by the first driving voltage generates a second driving voltage by an ESD current. A second electrostatic protection unit discharges the introduced ESD current into the power source supply pad by the second driving voltage such that a voltage applied to a gate of the first NMOS transistor is reduced.