An impedance calibration circuit includes a first calibration voltage driver configured to operate in response to a first enable signal, compare a first calibration voltage signal with a first reference voltage signal, and drive the first calibration voltage signal, a first control code generator configured to operate in response to a second enable signal, compare the first calibration voltage signal with a first target voltage signal, and generate a first control code signal, and a first reference voltage generator configured to generate the first reference voltage signal in response to the first control code signal.