The Commonwealth of Massachusetts (IPA: /ˌmæsəˈtʃuːsɨts/) is a state located in the New England region of the northeastern United States. Most of its population of 6.4 million live in the Boston metropolitan area. The eastern half of this relatively small state is mostly urban and suburban. The west is primarily rural, also with most of its population 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.

Massachusetts has been significant throughout American history. Plymouth was the second permanent English settlement in North America. Colonists from England founded many towns and villages in the present-day territory of Massachusetts very early in the nation's history in the 1620s and 1630s. The Boston area became known as the "Cradle of Liberty" for the ferment there which led to the American Revolution and the independence of the United States from Great Britain. Massachusetts was the first U.S. state to abolish slavery and was a center of the temperance movement and abolitionist activity in the years leading to the American Civil War. The state has contributed many prominent politicians to national service, including the Adams family and, more recently, the Kennedy family.

Originally dependent on agriculture and trade with Europe, Massachusetts was transformed into a manufacturing center during the Industrial Revolution. Migration of factories to the lower-wage Southern states caused economic stagnation during the first half of the 20th century. The economy of Massachusetts was revived after World War II, and today is prominent in higher education, health care, and high technology.