Nantucket is an island located in Massachusetts, United States, situated approximately 30 miles south of the Cape Cod peninsula. Along with the small islands of Tuckernuck and Muskeget, it constitutes the Town and County of Nantucket, which operates under a combined county and town government structure. As the southeasternmost town in Massachusetts, the island serves as both a distinct municipality and a unique administrative entity within the state.

European settlement began in earnest in 1659 when investors led by Tristram Coffin purchased the island from Thomas Mayhew. The area was originally part of Dukes County until Nantucket County was partitioned in 1695. Before 1795, the main settlement was known as Sherburne before being renamed the Town of Nantucket. The island holds significant heritage status, designated a National Historic Landmark District in 1966 for its architectural preservation.

The island features quiet harbors, dramatic cliffs, sandy beaches, and lighthouses alongside beautiful old mansions and gardens. It is recognized as the finest surviving example of a late 18th- and early 19th-century New England seaport town. Notable sites include the Whaling Museum and preserved lands managed by the Nantucket Conservation Foundation, which protects about 36 percent of the island's diverse ecosystems.

Nantucket is a tourist destination and summer colony known for five-star service, fine dining, and exclusive golf clubs. Visitors enjoy whale watching, bird watching, and seafood cuisine, with historical ties to the whaling industry and the Underground Railroad. The community also celebrates Indigenous People's Day, voted in by the Annual Town Meeting in 2021, reflecting its complex cultural history.

The permanent population was 14,255 as of 2020, swelling to around 80,000 during summer months due to seasonal residents and tourists. The local economy is driven by tourism and high-value real estate, with average single-family home prices reaching $2.3 million in early 2018. While accessible year-round, the island offers fewer services and limited ferry schedules during the off-season when the population dwindles.