An underbody unit for a motor vehicle body has a floor body (12) connectable to the motor vehicle body for dissipating static and/or dynamic loads. Reinforcing ribs (14) protrude up from the floor body (12). The reinforcing ribs (14) together with the floor body (12) delimit receiving pockets (16) for receiving battery cell units (18) of a traction battery for driving the motor vehicle. First and second connections (34, 36) supply and remove a liquid cooling medium for cooling the floor body (12). The battery cell units (18) are above the floor body (12) and can be inserted into the underbody unit (10). Thus, the underbody unit (10), the reinforcing ribs (14) and the connections (34, 36) for the coolant define a supporting plate that can support the heavy battery cell units (18), form armor plating for protection and a heat exchanger for active and/or passive cooling.