Battery pack

A battery pack includes a first battery module group including one or more battery modules, a second battery module group including one or more battery modules, and aligned with the first battery module group, a housing accommodating the first and second battery module groups therein, and a guide member between the first and second battery module groups, and adjacent to one of the battery modules of the first battery module group. The guide member divides a flow path of a heat exchange medium passing through the first battery module group.