Dorchester (colloquially referred to as Dot) is a Boston neighborhood comprising more than 6 square miles (16 km2) in the City of Boston, Massachusetts, United States. Originally, Dorchester was a separate town, founded by Puritans who emigrated in 1630 from Dorchester, Dorset, England to the Massachusetts Bay Colony. This dissolved municipality, Boston's largest neighborhood by far, is often divided by city planners in order to create two planning areas roughly equivalent in size and population to other Boston neighborhoods. The neighborhood is named after the town of Dorchester in the English county of Dorset, from which Puritans emigrated on the ship Mary and John, among others.

Founded in 1630, just a few months before the founding of the city of Boston, Dorchester now covers a geographic area approximately equivalent to nearby Cambridge.[6] It was still a primarily rural town and had a population of 12,000 when it was annexed to Boston in 1870. Railroad and streetcar lines brought rapid growth, increasing the population to 150,000 by 1920. In the 2010 United States Census, the neighborhood's population was 92,115. The Dorchester neighborhood has a very diverse population, which includes a large concentration of African Americans, European Americans (particularly those of Irish, German, and Polish origin), Caribbean Americans, Latinos, and East and Southeast Asian Americans. Dorchester also has a significant LGBT population, with active political groups and the largest concentration of same-sex couples in Boston after the South End and Jamaica Plain.

Most of the people over the age of 25 have completed high school or obtained a GED. Dorchester was originally inhabited by the Neponset/Neponsett tribe of the Massachusett nation. For generations, they made their home along the Neponset River estuary, which was a plentiful source of food due to the freshwater meeting the salt water. The Neponsett "concept of land ownership differed sharply from the European. The Massachusett did not own the land, but what was on it or what it produced. The Neponsett owned the shellfish beds, beaver, and trout from the marsh and river; the planting fields from the hillsides and the deer from the forests.

"As one of the first groups of Indigenous peoples to encounter English colonists, the Neponset people experienced a rapid decline in population in the 17th and 18th centuries due to violence perpetrated by the English and infectious diseases brought by the Europeans. The Massachusett leader, Chickatawbut, negotiated with the first settlers, but he died of smallpox in 1633, and his brother, Cutshamekin deeded further land to the settlers.[10] Despite several centuries of struggle due to European settlement, members of the Neponsett/Ponkapoag tribe continue to live in the Boston area and have established a tribal council