A memory system includes a memory module that includes a first memory device through a fourth memory device and a first error correction code (ECC) device, and a memory controller that exchanges first user data with each of the first memory device through the fourth memory device through 8 data lines and exchanges first ECC data with the first ECC device through 4 data lines. The memory controller includes an ECC engine that corrects a 32-random bit error of the first user data, based on the first ECC data.