Massachusetts Bay

Map of Massachusetts Bay.

The Massachusetts Bay, also called Mass Bay, is one of the largest bays of the Atlantic Ocean which forms the distinctive shape of the coastline of the U.S. state of Massachusetts. Its waters extend 65 miles (105 km) into the Atlantic Ocean.^{[citation needed]} Massachusetts Bay includes the Boston Harbor, Dorchester Bay, Quincy Bay (both part of the Outer Boston Harbor), and Hingham Bay. Massachusetts Bay is itself part of the Gulf of Maine, which reaches from Cape Cod up to Nova Scotia.

The bay is enclosed on the north by Cape Ann. Just south is Cape Cod Bay. Cape Cod Bay is sometimes construed as part of Massachusetts Bay; under this interpretation, the name "Massachusetts Bay" denotes the entire rectangular area of ocean between Cape Ann and Cape Cod. The bay's westernmost point is situated at Boston.

The bay gave its name to the Massachusetts Bay Colony, one of the two predecessor colonies of the current state of Massachusetts. Massachusetts Bay, along with Quincy Bay, Narragansett Bay, Buzzards Bay and Cape Cod Bay, is also one of the bays adjacent to Massachusetts that give the commonwealth the nickname "the Bay State".