Disclosed are various embodiments for distributed network address allocation management. In one embodiment, a first instance of a plurality of instances of an allocation management service assigns a first portion of a network address space to the first instance and a second portion of the network address space to a second instance of the plurality of instances. The second instance receives a request to allocate a particular network address block. The second instance allocates the particular network address block from the second portion of the network address space by updating an allocation data structure. An allocation of the particular network address block is returned in response to the request. A copy of the allocation data structure maintained by the first instance is updated asynchronously based at least in part on the allocation of the particular network address block.