Cape Cod Bay is a large bay of the Atlantic Ocean adjacent to the U.S. state of Massachusetts. Measuring 604 square miles (1,560 km2) below a line drawn from Brant Rock in Marshfield to Race Point in Provincetown, Massachusetts, it is enclosed by Cape Cod to the south and east, and Plymouth County, Massachusetts, to the west. To the north of Cape Cod Bay lie Massachusetts Bay and the Atlantic Ocean. Cape Cod Bay is the southernmost extremity of the Gulf of Maine. Cape Cod Bay is one of the bays adjacent to Massachusetts that give it the name Bay State. The others are Narragansett Bay, Buzzards Bay, and Massachusetts Bay.

Provincetown is a New England town located at the extreme tip of Cape Cod in Barnstable County, Massachusetts, in the United States. A small coastal resort town with a year-round population of 3,664 as of the 2020 United States Census, Provincetown has a summer population as high as 60,000. Often called "P-town" or "Ptown", the locale is known for its beaches, harbor, artists, tourist industry, and as a popular vacation destination for the LGBT+ community.