A semiconductor memory system includes a memory medium and a data input/output (I/O) pin repair control circuit. The memory medium includes a plurality of memory dies and a spare die. Each of the plurality of memory dies has a plurality of memory regions and a plurality of data I/O pins, and the spare die has a plurality of spare regions and a plurality of data I/O pins. The data I/O pin repair control circuit performs a repair process for replacing an abnormal data I/O pin among the plurality of data I/O pins included in any of the plurality of memory dies with a data I/O pin of the plurality of data I/O pins included in the spare die.