Lagoa Guaíba, often referred to as Guaíba Lake or River, is a large navigable water body in Rio Grande do Sul, Brazil, forming a prominent feature of the Porto Alegre cityscape. It is connected to the Atlantic Ocean via Lagoa dos Patos to the south. The shoreline in Porto Alegre, known as the Orla do Guaíba, is developed with a promenade, bicycle paths, piers, and parks, offering significant urban access for paddlers. A key paddling access point is the area around Praça Montevideo, and the waterfront promenade provides a continuous route for launching and landing, with paths running from Parque Marinha do Brasil to the Hipódromo do Cristal. The overall character is that of a major urban waterway, with the city skyline providing a constant backdrop and famous sunsets being a notable attraction.

The water body is used for various recreational activities, including boat tours that offer panoramic views of the city. While specific paddling regulations are not detailed, the presence of commercial boat traffic indicates paddlers should be mindful of larger vessels. The shoreline features several tourist sights, including the Gasometer cultural center, beaches, and an amphitheater. The water is described as very large, which can lead to open water conditions.