A shunt regulator includes a control circuit, a bypass circuit and a protection circuit. The control circuit is coupled between a first node and a ground, and generates a gate control signal in response to a voltage of the first node and a reference voltage. The bypass circuit forms a first current path between the first node and the ground in response to the gate control signal. The protection circuit has an MOS transistor that is fully turned on in response to a current flowing through the bypass circuit, and forms a second current path between the first node and the ground. Therefore, the shunt regulator occupies a relatively small area in an integrated circuit.