A memory device includes a memory cell array, a row decoder, a multi-column decoder, a gating circuit, and an input/output data driving circuit. The memory cell array includes a plurality of memory cells arranged to form a plurality of rows and a plurality of columns. The row decoder generates a row selection signal based on a row address to select a target row from the rows. The multi-column decoder generates a multi-column selection signal based on a column address and column selection information to select a plurality of target columns from columns included in the target row at a time. The gating circuit selects the target columns at a time based on the multi-column selection signal. The input/output data driving circuit writes input data to the target columns at a time or outputs data stored in the target columns at a time as output data through the gating circuit based on the multi-column selection signal and a data mask signal. Column addresses corresponding to the target columns included in the target row are not consecutive.