A display device according to an embodiment of the inventive concept includes a data driving unit, a gate driving unit, a signal control unit for controlling driving of the data driving unit and the gate driving unit, and a display panel. The data driving unit generates an internal clock signal for outputting data voltages corresponding to image data, and the display panel displays an image corresponding to the data voltages in response to a gate driving signal outputted from the gate driving unit. The data driving unit includes a filtering unit for converting a first frequency control signal received from the signal control unit so as to generate a second frequency control signal, and a clock training unit for training a clock signal received from the signal control unit so as to generate the internal clock signal in response to the second frequency control signal.