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Saint Lawrence Boulevard (officially in French: Boulevard Saint-Laurent) is a major street in Montreal, Quebec, Canada. A commercial artery and cultural heritage site, the street runs north-south through the near-centre of city and is nicknamed The Main which is the abbreviation for "Main Street" and in French La Main.

Beginning at De la Commune Street at the edge of the Saint Lawrence River, it transects the Island of Montreal, passing through the boroughs of Ville-Marie, Le Plateau-Mont-Royal, Rosemont—La Petite-Patrie, Villeray–Saint-Michel–Parc-Extension, and Ahuntsic-Cartierville to Rue Somerville at the edge of the Rivière des Prairies – a total length of about 11.25 km.

Saint Laurent Boulevard became a boulevard in 1905 and is often referred to as The Main. It serves as the city's physical division of east and west (in Montreal parlance; in reality east is more like north-northeast and west is south-southwest). Street numbers begin at Saint Lawrence and continue outward, with street names being suffixed by Ouest (West) or Est (East), depending on their orientation.

The boulevard traditionally divides Montreal by language, ethnicity, and class. Saint Laurent Boulevard was for generations the symbolic dividing line for the city, with the predominantly English-speaking population to the west, French-speaking population to the east, and immigrant communities in between along the Main and Park Avenue. The Main runs through many of Montreal's ethnic communities, a first stop for immigrant communities for over 100 years — initially Jewish, Chinese and Italian, and later Portuguese, Greek, Arab, Haitian and others.

The southern section of the boulevard in downtown Montreal and the Plateau is lined with trendy shops and restaurants, and is the site of many street-fairs and festivals. What were once run-down factories have been turned into expensive lofts. Saint Laurent Boulevard is representative of Montreal's shift out of the economic decline in the 1980s and 90s.

In 2002 the Historic Sites and Monuments Board of Canada named Saint Lawrence Boulevard as The Main National Historic Site of Canada. Then Minister of Heritage, Sheila Copps, speaking at the ceremony, said: "our country does not belong to just two founding peoples. It belongs to all Canadians. [This is] a first step toward a new story of Canada that includes all of our partners as equals."

The Jewish community on the Main sprang up after the heavy immigration of the early to mid-1900s. Jewish settlement occurred first on the lower Main, in a section that now is part of Montreal's Chinatown.

By 1871 a Jewish enclave numbering just over 400 people had formed by the corner of St. Lawrence and Dorchester Street, with the first Jewish educational institution, the Talmud Torah, located at the corner of Saint Urbain Street and De la Gauchetière Street. Middle-class members of the community were already beginning to move up the Main towards Sherbrooke and Prince Arthur Streets, while further west, a small number of well-off Jews lived near McGill University.

Numerous art galleries and other cultural organizations make their home on the Main. including La Centrale/Powerhouse (Canada's oldest women's artist-run centre), Théâtre Espace Go (since 1995), Ethnik-art, the Festival du Nouveau Cinéma, Festival International Nuits d'Afrique, the Montreal Fringe Festival, Image & Nation Festival, My Hero Gallery, the Society for Arts and Technology and Sensation Mode. Many well-known music venues can be found on the Main, including Casa del Popolo, Sala Rosa, Club Soda, Barfly, Jupiter Room, Main Hall, Club Lambi, The Academy Club and Divan Orange. The street is also home to the National Theatre School of Canada as well as the EXcentris arts complex, adjacent to the offices of Softimage. Gastronomic highlights include Schwartz's deli and the nearby Main Deli Steak House, both serving Montreal-style smoked meat, as well as the Montreal Pool Room, serving Montreal hot dogs since 1912.