The Commonwealth of Massachusetts (often simply, "Massachusetts") is a state in the New England region of the northeastern United States. Most of its population of 6.4 million lives in the Boston metropolitan area. The eastern half of this relatively small state is mostly urban and suburban. The west is primarily rural; however, most of its population actually lives in urban enclaves. Massachusetts is the most populous of the six New England states and ranks third in overall population density among the 50 states.

The first Europeans to settle New England landed in present-day Massachusetts. These settlers were Pilgrims and Puritans from England seeking religious freedom. They founded Plymouth, Salem, and Boston, which soon became the hub of the region, then the Pioneer Valley along the Connecticut River where the state's best agricultural land was concentrated. A century and a half later, Massachusetts became known as the 'Cradle of Liberty' for the revolutionary ferment in Boston that helped spawn the war of the Thirteen Colonies for independence.

During the 19th century, Massachusetts transformed itself from a mainly agricultural economy to a manufacturing one, making use of its many rivers for power to operate factories for shoes, furniture, and clothing that drew labor from Yankees on unproductive subsistence farms at first, then turned to immigrant labor from Europe. The industrial economy declined in the early twentieth century when industry moved south in search of cheaper labor. A revitalization came in the 1970s when, nourished by the graduates of the area's many elite institutions of higher education, the Boston suburbs (particularly those near Route 128) became home to dozens of high-technology companies. Massachusetts's colleges and universities, as well as its technology sectors, continue to thrive.

Massachusetts has been one of the most influential states in America. The first battles of the American Revolution were fought in the Massachusetts towns of Concord and Lexington. The Boston Tea Party is a well-known example of the revolutionary spirit of those times. In the 19th century, the state became a bastion of social progressivism and a birthplace of the abolitionist movement that emancipated southern blacks from slavery. The Kennedy family dominated Massachusetts politics in the 20th century. In the 21st century, the state continues to lead the country in social and cultural change, and in 2004 became the first state in the union to allow same-sex couples to marry.