According to one embodiment, a controller of a memory system executes a first write operation of writing write data into a first storage region, in response to reception of one or more write requests for specifying a first zone from a host, during a period from execution of an erase operation of the first storage region until a first time elapses. When the first time has elapsed after execution of the erase operation, in a state in which an unwritten region having a size larger than or equal to a first size remains in the first storage region, the controller does not execute the first write operation, allocates the first storage region as a nonvolatile buffer capable of temporarily storing write data to be written to each of a plurality of zones.