A memory device includes a base die that includes a data signal bump configured to receive a data signal, a first memory stack that includes first memory dies sequentially stacked on the base die, and a second memory stack that includes second memory dies sequentially stacked on the base die and spaced from the first memory stack in a direction parallel to an upper surface of the base die. The base die is configured to selectively provide the data signal received through the data signal bump to one of the first memory stack or the second memory stack based on a selection signal.