Founded in 1695, Nantucket County is one of 14 counties in the state of Massachusetts. Historically, Nantucket County was formed from Nantucket Island which had been part of Dukes County, New York until Massachusetts gained it in 1691. The city of Nantucket is the county seat. With FIPS code of 19, Nantucket County has a population of 14,491 and area of 48 square miles (124 km2).
List of all cities in Nantucket County, MA alphabetically
| City/Town | Postal Code | Area Code |
| Nantucket, MA | 02554 | 508/774 |
| 02564 | 508/774 | |
| 02584 | 508/774 | |
| Sconset, MA | 02564 | 508/774 |
| Siasconset, MA | 02564 | 508/774 |