Lago Budi is a brackish, tidal lake situated near the Pacific coast in the La Araucanía Region of southern Chile, straddling the boundary between the Saavedra and Teodoro Schmidt communes. Its name derives from the Mapudungun word "Füzi," meaning salt. The lake covers a surface area of 56.2 square kilometers, with a shoreline of approximately 105 kilometers and a maximum depth of 10.5 meters. It sits at an elevation of just 2 meters above sea level.

Unlike the majority of Chilean lakes, Lago Budi is not of glacial origin and lies outside the Andes mountain range. It formed through tectonic movements and eustatic sea level changes, and occupies a coastal plain just south of the Nahuelbuta Range and north of the Valdivian Coastal Range, where the Chilean Coast Range is notably low. It is considered one of the few lakes along the entire west coast of the Americas that receives seasonal inflows of seawater, giving it a brackish character that distinguishes it from the freshwater lakes more commonly associated with the region.

The lake drains via the Budi River, while its primary inflows are the Estero Comoe and Estero Boyeco. The main settlement on its shores is Puerto Domínguez. Kayaking is an established activity on the lake, and paddlers can expect to encounter black-necked swans among the wildlife present on the water. The broader coastal area, known as the Lafkenche coast, carries significant cultural importance as the homeland of the Lafkenche Mapuche people, whose relationship with the sea and lake environment is a defining feature of the region.

The nearby town of Puerto Saavedra offers access to marine gastronomy and cultural experiences. Given the lake's tidal connection to the sea, paddlers should be aware of the brackish water conditions and the potential influence of tidal fluctuations on water levels and currents. Summer is noted as a favorable time to visit and explore the lake.