Represa Guarapiranga is a large freshwater reservoir located in the southern zone of São Paulo, sitting at an elevation of approximately 738 meters. Originally constructed in 1906 by the São Paulo Tramway, Light and Power Company to supply electricity to the Parnaíba Hydroelectric plant, it was completed in 1908 and began serving as a potable water reservoir in 1928. The reservoir is fed by the Rio Guarapiranga and several smaller rivers and streams passing through the municipalities of São Paulo, Itapecerica da Serra, and Embu-Guaçu. It is currently managed by SABESP for the water supply of Greater São Paulo and also functions as a flood control mechanism.

The reservoir sits close to the Autódromo de Interlagos, the Formula 1 circuit, and is accessible by car via Marginal Pinheiros, Av. Nações Unidas, and Av. Interlagos. Several clubs along the shoreline provide access to the water, along with amenities including rescue services, showers, toilets, food, and parking. A daily fee of approximately US$13 is charged at these clubs, which includes rescue coverage. The shoreline is largely grassed rather than sandy beach.

Water conditions are generally flat to choppy, making the reservoir suitable for intermediate to expert water-sport users. Prevailing winds come from the south and southwest, with SW being the most favorable direction. The best season runs from winter through spring, roughly June to October. During this period, air temperatures typically range between 18°C and 26°C, while water temperatures fall between 10°C and 15°C — a short wetsuit is recommended. A typical winter afternoon brings overcast skies, air temperatures around 18°C, and water temperatures near 12°C.

The reservoir has artificial beaches and marinas in its peripheral areas. Fishing is also practiced on the water, with species including trahira, redbreast tilapia, San Francisco piranha, and black pacu found in the area. Paddlers sharing the water with motorized boats should be aware of vessel traffic. The reservoir is an important part of São Paulo's urban water infrastructure, and its proximity to one of Latin America's largest cities means the surrounding area is heavily developed, though the water itself is clean.