Remembering often requires the selection of goal-relevant memories in the face of competition from irrelevant memories. Although there is a cost of selecting target memories over competing memories (increased forgetting of the competing memories), here we report neural evidence for the adaptive benefits of forgetting--namely, reduced demands on cognitive control during future acts of remembering. Functional magnetic resonance imaging during selective retrieval showed that repeated retrieval of target memories was accompanied by dynamic reductions in the engagement of functionally coupled cognitive control mechanisms that detect (anterior cingulate cortex) and resolve (dorsolateral and ventrolateral prefrontal cortex) mnemonic competition. Strikingly, regression analyses revealed that this prefrontal disengagement tracked the extent to which competing memories were forgotten; greater forgetting of competing memories was associated with a greater decline in demands on prefrontal cortex during target remembering. These findings indicate that, although forgetting can be frustrating, memory might be adaptive because forgetting confers neural processing benefits.