South Boston is a densely populated neighborhood of Boston, Massachusetts, located south and east of the Fort Point Channel and abutting Dorchester Bay. South Boston, colloquially known as Southie, has undergone several demographic transformations since being annexed to the city of Boston in 1804. The neighborhood, once primarily farmland, is popularly known by its twentieth century identity as a working class Irish Catholic community. Throughout the twenty-first century, the neighborhood has become increasingly popular with millennial professionals. South Boston contains Dorchester Heights, where George Washington forced British troops to evacuate during the American Revolutionary War.

South Boston has undergone gentrification, and consequently, its real estate market has seen property values join the highest in the city. South Boston has also left its mark on history with Boston busing desegregation. South Boston is also home to the St. Patrick's Day Parade, a celebration of the Irish-American culture and the Evacuation Day observance. Geographically, Dorchester Neck was an isthmus, a narrow strip of land that connected the mainland of the colonial settlement of Dorchester with Dorchester Heights. Landfill has since greatly increased the amount of land on the eastern side of the historical neck, and widened the connection to the mainland to the point that South Boston is no longer considered separate from it. South Boston gained an identity separate from Dorchester, but the two were annexed by Boston in pieces, from 1804 to 1870. \

During the American Revolutionary War, George Washington placed a cannon on Dorchester Heights, thereby forcing the evacuation of British troops from Boston on March 17, 1776. The British evacuated Boston and Fort William and Mary for Halifax, Nova Scotia. Fort William and Mary was replaced with a brick fortification known as Fort Independence. That fort was replaced by a granite fortification (bearing the same name) prior to the American Civil War, and still stands on Castle Island as a National Historic Landmark. Edgar Allan Poe was stationed at Castle Island for five months in 1827 and was inspired to write The Cask of Amontillado based on an early Castle Island legend. During the 1970s, South Boston received national attention for its opposition to court-mandated school (de facto) desegregation by busing students to different neighborhoods. In the early 21st century, property values, especially in the City Point neighborhood near Castle Island, rose to the level of some of the highest in the city.

The City Point area of South Boston, labeled "East Side" by realtors, has seen a major increase in property values due to its close proximity to downtown Boston and gentrification.[citation needed] The "West Side" of South Boston, also known as the "lower end" by lifelong residents, though slower to begin the gentrification process also benefits from the proximity to not only downtown but also the popular South End. Additionally, the West Side is home to the first green residence (Gold LEED certified) in Boston — the Macallen Building which was featured in the movie The Greening of Southie. The City of Boston is investing in the West Side through developments like the ~150,000-square-foot (14,000 m2) mixed use (residential and commercial) building being developed by the Boston Redevelopment Authority on West Broadway.