Represa Do Rio Manso is a large hydroelectric reservoir located in the state of Mato Grosso, Brazil, approximately 86 kilometres from Cuiabá, the state capital, accessible via good roads. The dam impounds the Manso River, a tributary of the Cuiabá River, along with the Roncador River and Casca River. The reservoir sits at roughly 360 metres above sea level and spans the municipalities of Chapada dos Guimarães and Rosário Oeste in the midwest region of Mato Grosso. The dam itself stands 72 metres high with a length of 3,680 metres and was completed in 1999.

The reservoir has developed into a recognized tourist destination. Known access points include Marina Portal Das Aguas and Marina Do Sol, both of which serve as water access points for recreational use on the lake.

Water quality is a concern worth noting. The submerged and decaying vegetation resulting from the original flooding has had a negative impact on water quality both within the reservoir and downstream of the dam, and this has affected edible fish stocks. Paddlers should be aware of this ongoing water quality issue when planning trips.

The reservoir is well known for sport fishing, particularly for tucunaré (peacock bass), which are found in notable numbers and size. Fishing operations on the lake include guided services and bass boat rentals. Nearby fishing waters include Rio Cuiabá approximately 44 miles away, Córrego Jacarezinho about 21 miles away, and Rio Da Casca roughly 31 miles away.

Brazil's recreational fishing regulations, including closed-season (defeso/piracema) periods specific to the river basin and species, apply to the reservoir. Access to the water body is governed by Brazilian water-domain law, with inland waters regulated at the federal or state level depending on their classification.