There are provided a level shifter and a memory system including the same. The level shifter includes: a pull-up unit for supplying an internal power supply voltage to a first output node or a second output node in response to an input signal and an inverted input signal; a pull-down unit for applying a ground voltage to the first output node or the second output node in response to potential levels of the first output node and the second output node; and a discharge unit for discharging the potential level of the first output node or the second output node in response to the input signal and the inverted input signal.