The Massachusetts Bay Colony (1628–1691), more formally the Colony of Massachusetts Bay, was an English settlement on the east coast of North America around the Massachusetts Bay, one of the several colonies later reorganized as the Province of Massachusetts Bay. The lands of the settlement were in southern New England, with initial settlements on two natural harbors and surrounding land about 15.4 miles (24.8 km) apart—the areas around Salem and Boston, north of the previously established Plymouth Colony. The territory nominally administered by the Massachusetts Bay Colony covered much of central New England, including portions of Massachusetts, Maine, New Hampshire, and Connecticut.

The Province of Massachusetts Bay was a colony in New England which became one of the thirteen original states of the United States. It was chartered on October 7, 1691, by William III and Mary II, the joint monarchs of the kingdoms of England, Scotland, and Ireland, and was based in the merging of several earlier British colonies in New England. The charter took effect on May 14, 1692, and included the Massachusetts Bay Colony, the Plymouth Colony, the Province of Maine, Martha's Vineyard, Nantucket, Nova Scotia, and New Brunswick; the Commonwealth of Massachusetts is the direct successor. Maine has been a separate state since 1820, and Nova Scotia and New Brunswick are now Canadian provinces, having been part of the colony only until 1697.