Club Atlético San Lorenzo de Almagro, commonly known as San Lorenzo de Almagro or simply San Lorenzo (in English: Saint Lawrence), is a sports club of Argentina in the Boedo district of Buenos Aires. It is best known for its football team, which plays in the Primera División, the first tier of the Argentinian football league system. San Lorenzo is also considered one of the "big five" ("Los 5 Grandes") of Argentinian football, along with Independiente, River Plate, Boca Juniors, and Racing Club.

San Lorenzo plays its home games at Estadio Pedro Bidegain, popularly known as Nuevo Gasómetro. The stadium and sports facilities are located in the Bajo Flores district of the Buenos Aires. The club's previous stadium was the Viejo Gasómetro, located in Boedo. In 1979, the Gasómetro was expropriated by the de facto Government of Argentina and then sold to supermarket chain Carrefour. The club currently has six headquarters: three in Boedo, one in Monserrat, one at Bajo Flores, and one in villa Gesell. San Lorenzo also plans to expand its main seat on La Plata Avenue, while a 15-hectare campus in Ezeiza is projected to develop an olympic football program.

San Lorenzo's historical rival is Huracán, located in Parque Patricios. The two clubs play one of the older derbies in Argentina. Some supporters consider this derby as the third-most important after Superclásico and Clásico de Avellaneda, in addition to being one of the most uneven derbies of Argentine Football.

Other sports practised at the club are artistic roller skating, basketball, field hockey, futsal, handball, martial arts, roller hockey, swimming, tennis, and volleyball. Some years ago, San Lorenzo had also opened a rugby union section, but it is no longer active. San Lorenzo gained international recognition in March 2013 with the election of Pope Francis, a supporter and socio (member) of the club. The players played with the Pope's photo on their shirts during a league match against Colón on 16 March 2013.