- Micronesia (UK: /?ma?kr?’ni?zi?/, US: /-’ni???/) is a subregion of Oceania, consisting of approximately 2,000 small islands in the Northwestern Pacific Ocean. It has a close shared cultural history with three other island regions: Maritime Southeast Asia to the west, Polynesia to the east, and Melanesia to the south�as well as with the wider community of Austronesian peoples.